CVE-2026-33671: Picomatch Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-c2c7-rcm5-vvqj",
  "modified" : "2026-03-27T21:36:13Z",
  "published" : "2026-03-25T21:12:07Z",
  "aliases" : [ "CVE-2026-33671" ],
  "summary" : "Picomatch has a ReDoS vulnerability via extglob quantifiers",
  "details" : "### Impact\n`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.\n\nExamples 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.\n\nApplications 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.\n\n### Patches\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\nIf upgrading is not immediately possible, avoid passing untrusted glob patterns to `picomatch`.\n\nPossible mitigations include:\n- disable extglob support for untrusted patterns by using `noextglob: true`\n- reject or sanitize patterns containing nested extglobs or extglob quantifiers such as `+()` and `*()`\n- enforce strict allowlists for accepted pattern syntax\n- run matching in an isolated worker or separate process with time and resource limits\n- apply application-level request throttling and input validation for any endpoint that accepts glob patterns\n\n### Resources\n- Picomatch repository: https://github.com/micromatch/picomatch\n- `lib/parse.js` and `lib/constants.js` are involved in generating the vulnerable regex forms\n- Comparable ReDoS precedent: CVE-2024-4067 (`micromatch`)\n- Comparable generated-regex precedent: CVE-2024-45296 (`path-to-regexp`)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "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-c2c7-rcm5-vvqj"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33671"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/micromatch/picomatch/commit/5eceecd27543b8e056b9307d69e105ea03618a7d"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/micromatch/picomatch"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1333" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-25T21:12:07Z",
    "nvd_published_at" : "2026-03-26T22:16:30Z"
  }
}