CVE-2026-33672: Picomatch Method Injection Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3v7f-55p6-f55p",
  "modified" : "2026-03-27T21:36:24Z",
  "published" : "2026-03-25T21:13:39Z",
  "aliases" : [ "CVE-2026-33672" ],
  "summary" : "Picomatch: Method Injection in POSIX Character Classes causes incorrect Glob Matching",
  "details" : "### Impact\npicomatch 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.\n\nThis 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.\n\nAll users of affected `picomatch` versions that process untrusted or user-controlled glob patterns are potentially impacted.\n\n### Patches\n\nThis issue is fixed in picomatch 4.0.4, 3.0.2 and 2.3.2.\n\nUsers should upgrade to one of these versions or later, depending on their supported release line.\n\n### Workarounds\n\nIf upgrading is not immediately possible, avoid passing untrusted glob patterns to picomatch.\n\nPossible mitigations include:\n- Sanitizing or rejecting untrusted glob patterns, especially those containing POSIX character classes like `[[:...:]]`.\n- Avoiding the use of POSIX bracket expressions if user input is involved.\n- Manually patching the library by modifying `POSIX_REGEX_SOURCE` to use a null prototype:\n\n  ```js\n  const POSIX_REGEX_SOURCE = {\n    __proto__: null,\n    alnum: 'a-zA-Z0-9',\n    alpha: 'a-zA-Z',\n    // ... rest unchanged\n  };\n  \n### Resources\n\n- fix for similar issue: https://github.com/micromatch/picomatch/pull/144\n- picomatch repository https://github.com/micromatch/picomatch",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "picomatch"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.0.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "picomatch"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.0.0"
      }, {
        "fixed" : "3.0.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "picomatch"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.3.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/micromatch/picomatch/security/advisories/GHSA-3v7f-55p6-f55p"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33672"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/micromatch/picomatch/commit/4516eb521f13a46b2fe1a1d2c9ef6b20ddc0e903"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/micromatch/picomatch"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-25T21:13:39Z",
    "nvd_published_at" : "2026-03-26T22:16:30Z"
  }
}