Impact

picomatch is vulnerable to Regular Expression Denial of Service (ReDoS) when processing crafted extglob patterns. Certain patterns using extglob quantifiers such as +() and *(), especially when combined with overlapping alternatives or nested extglobs, are compiled into regular expressions that can exhibit catastrophic backtracking on non-matching input.

Examples of problematic patterns include +(a|aa), +(*|?), +(+(a)), *(+(a)), and +(+(+(a))). In local reproduction, these patterns caused multi-second event-loop blocking with relatively short inputs. For example, +(a|aa) compiled to ^(?:(?=.)(?:a|aa)+)$ and took about 2 seconds to reject a 41-character non-matching input, while nested patterns such as +(+(a)) and *(+(a)) took around 29 seconds to reject a 33-character input on a modern M1 MacBook.

Applications are impacted when they allow untrusted users to supply glob patterns that are passed to picomatch for compilation or matching. In those cases, an attacker can cause excessive CPU consumption and block the Node.js event loop, resulting in a denial of service. Applications that only use trusted, developer-controlled glob patterns are much less likely to be exposed in a security-relevant way.

Patches

This issue is fixed in picomatch 4.0.4, 3.0.2 and 2.3.2.

Users should upgrade to one of these versions or later, depending on their supported release line.

Workarounds

If upgrading is not immediately possible, avoid passing untrusted glob patterns to picomatch.

Possible mitigations include:

• disable extglob support for untrusted patterns by using noextglob: true
• reject or sanitize patterns containing nested extglobs or extglob quantifiers such as +() and *()
• enforce strict allowlists for accepted pattern syntax
• run matching in an isolated worker or separate process with time and resource limits
• apply application-level request throttling and input validation for any endpoint that accepts glob patterns

Resources

• Picomatch repository: https://github.com/micromatch/picomatch
• lib/parse.js and lib/constants.js are involved in generating the vulnerable regex forms
• Comparable ReDoS precedent: CVE-2024-4067 (micromatch)
• Comparable generated-regex precedent: CVE-2024-45296 (path-to-regexp)

Impact

picomatch is vulnerable to a method injection vulnerability (CWE-1321) affecting the POSIX_REGEX_SOURCE object. Because the object inherits from Object.prototype, specially crafted POSIX bracket expressions (e.g., [[:constructor:]]) can reference inherited method names. These methods are implicitly converted to strings and injected into the generated regular expression.

This leads to incorrect glob matching behavior (integrity impact), where patterns may match unintended filenames. The issue does not enable remote code execution, but it can cause security-relevant logic errors in applications that rely on glob matching for filtering, validation, or access control.

All users of affected picomatch versions that process untrusted or user-controlled glob patterns are potentially impacted.

Patches

This issue is fixed in picomatch 4.0.4, 3.0.2 and 2.3.2.

Users should upgrade to one of these versions or later, depending on their supported release line.

Workarounds

If upgrading is not immediately possible, avoid passing untrusted glob patterns to picomatch.

Possible mitigations include:

• Sanitizing or rejecting untrusted glob patterns, especially those containing POSIX character classes like [[:...:]].

• Avoiding the use of POSIX bracket expressions if user input is involved.

• Manually patching the library by modifying POSIX_REGEX_SOURCE to use a null prototype:

  const POSIX_REGEX_SOURCE = {
    __proto__: null,
    alnum: 'a-zA-Z0-9',
    alpha: 'a-zA-Z',
    // ... rest unchanged
  };

Resources

• fix for similar issue: fix: exception when glob pattern contains constructor micromatch/picomatch#144
• picomatch repository https://github.com/micromatch/picomatch

Impact

If pdf.js is used to load a malicious PDF, and PDF.js is configured with isEvalSupported set to true (which is the default value), unrestricted attacker-controlled JavaScript will be executed in the context of the hosting domain.

Patches

The patch removes the use of eval:
mozilla/pdf.js#18015

Workarounds

Set the option isEvalSupported to false.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1893645

The max option was being applied too late:

When expanding a single large numeric range like {1..10000000}, the sequence generation loop generates all 10 million intermediate elements before the max limit is applied With max=10, the output is correctly limited to 10 items, but the process still allocates ~505 MB and spends ~800ms building the full intermediate array.

Workaround

Ensure the string to be expanded doesn't contain more values than the desired max item count.

Impact

A brace pattern with a zero step value (e.g., {1..2..0}) causes the sequence generation loop to run indefinitely, making the process hang for seconds and allocate heaps of memory.

The loop in question:

https://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L184

test() is one of

https://github.com/juliangruber/brace-expansion/blob/daa71bcb4a30a2df9bcb7f7b8daaf2ab30e5794a/src/index.ts#L107-L113

The increment is computed as Math.abs(0) = 0, so the loop variable never advances. On a test machine, the process hangs for about 3.5 seconds and allocates roughly 1.9 GB of memory before throwing a RangeError. Setting max to any value has no effect because the limit is only checked at the output combination step, not during sequence generation.

This affects any application that passes untrusted strings to expand(), or by error sets a step value of 0. That includes tools built on minimatch/glob that resolve patterns from CLI arguments or config files. The input needed is just 10 bytes.

Patches

Upgrade to versions

• 5.0.5+

A step increment of 0 is now sanitized to 1, which matches bash behavior.

Workarounds

Sanitize strings passed to expand() to ensure a step value of 0 is not used.

Summary

Address6.group() and Address6.link() do not HTML-escape attacker-controlled content before embedding it in the HTML strings they return, and AddressError.parseMessage (emitted by the Address6 constructor for invalid input) can contain unescaped attacker-controlled content in one branch. An application that (1) passes untrusted input to Address6 and (2) renders the output of these methods, or the thrown error's parseMessage, as HTML (e.g. via innerHTML) is vulnerable to cross-site scripting. A related issue in v6.helpers.spanAll() produced malformed markup but was not exploitable; it is hardened in the same release for consistency.

Details

Four related issues were identified and fixed together:

1. Address6.group(): zone ID injection. The Address6 constructor stores the raw input (including any IPv6 zone ID) in this.address before zone stripping. group() then passed this.address to helpers.simpleGroup(), which wrapped each :-separated segment in a <span> element without HTML-escaping the content. A zone ID containing HTML markup was embedded verbatim.
2. Address6.link({ prefix, className }): attribute-value injection. link() concatenated user-supplied prefix and className into the href="…" and class="…" attributes without escaping. A caller passing untrusted content through these options could inject event handlers (e.g. onmouseover) and achieve XSS.
3. Address6 constructor: leading-zero IPv4 error path. The leading-zero branch in parse4in6() built AddressError.parseMessage by concatenating the raw address through String.replace(). Because parse4in6() runs before the bad-character check, any characters in the groups preceding the IPv4 suffix flowed into the error's HTML unescaped. Consumers who render parseMessage as HTML (its documented purpose — it already contains <span class="parse-error"> markup) could be XSS'd by a crafted input such as <img src=x onerror=alert(1)>:10.0.01.1.
4. v6.helpers.spanAll(): attribute-value injection (defense in depth). spanAll() embedded each character of its input into a class="digit value-${n} …" attribute without escaping. Because split('') limits n to a single character this was not exploitable in practice, but it produced malformed markup and is fixed for consistency.

Affected Versions

All versions up to and including 10.1.0.

Patched Version

10.1.1.

Impact

Real-world exposure is believed to be extremely limited. Analysis of all 425 dependent npm packages as well as GitHub code search found zero consumers of group(), link(), or spanAll(): these HTML-emitting surfaces appear to be unused across published npm packages and public repositories. Applications using only the address-parsing and comparison APIs (isValid, correctForm, isInSubnet, bigInt, etc.) are not affected.

Consumers who do render the output of group(), link(), spanAll(), or AddressError.parseMessage as HTML against untrusted input should upgrade.

PoC

const { Address6 } = require('ip-address');
const addr = new Address6('fe80::1%<img src=x onerror=alert(1)>');
document.body.innerHTML = addr.group();  // fires the onerror handler in 10.1.0

Workarounds

If users cannot upgrade immediately:

• Do not pass untrusted input to the Address6 constructor, or
• Never render the output of group(), link(), or spanAll(), nor the parseMessage field of any thrown AddressError, as HTML; treat these values as text only, or run them through DOMPurify before inserting into the DOM (DOMPurify's default configuration preserves the library's intended <span> wrapping while stripping any injected event handlers), or
• Validate input with Address6.isValid() and reject anything that contains a zone identifier (a % character) or characters outside [0-9a-fA-F:/] before passing it to the constructor.

Lack of separate CVEs

Given the evidence that these methods are not used, and given that they are all of the same construction, maintainers do not think it's relevant or useful to create a separate CVE for each library method.

Credit

ip-address thanks @scovetta for reporting this issue.