GHSA-3v7f-55p6-f55p

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GHSA-3v7f-55p6-f55p

Summary: Picomatch: Method Injection in POSIX Character Classes causes incorrect Glob Matching

Details: ### 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: ```js const POSIX_REGEX_SOURCE = { __proto__: null, alnum: 'a-zA-Z0-9', alpha: 'a-zA-Z', // ... rest unchanged }; ### Resources - fix for similar issue: https://github.com/micromatch/picomatch/pull/144 - picomatch repository https://github.com/micromatch/picomatch

References: https://github.com/micromatch/picomatch/security/advisories/GHSA-3v7f-55p6-f55p, https://nvd.nist.gov/vuln/detail/CVE-2026-33672, https://github.com/micromatch/picomatch/commit/4516eb521f13a46b2fe1a1d2c9ef6b20ddc0e903, https://github.com/micromatch/picomatch