# CVE-2026-33672: Picomatch: Method Injection in POSIX Character Classes causes incorrect Glob Matching

CVE-2026-33672 is fixed in node-anymatch on 1 platform by DEBIAN-CVE-2026-33672 (version 3.1.3+~cs8.0.6-1), released March 26, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-33672
- Priority: Routine
- CVSS: 5.3 (Moderate)
- EPSS: 0.0043
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 26, 2026
- Weakness: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-33672

## Description

Picomatch is a glob matcher written JavaScript. Versions prior to 4.0.4, 3.0.2, and 2.3.2 are vulnerable to a method injection vulnerability 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. 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. 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; and manually patching the library by modifying `POSIX_REGEX_SOURCE` to use a null prototype.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | node-anymatch Debian 14 | 3.1.3+~cs8.0.6-1 | [DEBIAN-CVE-2026-33672](https://patchblox.com/security/data/fix/linux/debian-cve-2026-33672.md) | Mar 26, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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