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BREW-AIDER-CVE-2021-27291 (GHSA-PQ64-V7F5-GQH8)

Vulnerability from osv_homebrew – Published: 2026-08-13 16:35 – Updated: 2026-09-09 23:40 – Source website
VLAI
Summary
Pygments vulnerable to Regular Expression Denial of Service (ReDoS)
Details

In pygments 1.1+, fixed in 2.7.4, the lexers used to parse programming languages rely heavily on regular expressions. Some of the regular expressions have exponential or cubic worst-case complexity and are vulnerable to ReDoS. By crafting malicious input, an attacker can cause a denial of service.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "pygments",
        "resource_purl": "pkg:pypi/pygments@2.19.2",
        "upstream_fixed_in": "2.7.4"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "aider",
        "purl": "pkg:brew/aider"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.86.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/pygments@2.19.2",
        "name": "pygments",
        "resource": "pygments",
        "strategy": "registry",
        "subject_version": "2.19.2"
      }
    ]
  },
  "details": "In pygments 1.1+, fixed in 2.7.4, the lexers used to parse programming languages rely heavily on regular expressions. Some of the regular expressions have exponential or cubic worst-case complexity and are vulnerable to ReDoS. By crafting malicious input, an attacker can cause a denial of service.",
  "id": "BREW-aider-CVE-2021-27291",
  "modified": "2026-09-09T23:40:56Z",
  "published": "2026-08-13T16:35:12Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-27291"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pygments/pygments/commit/2e7e8c4a7b318f4032493773732754e418279a14"
    },
    {
      "type": "WEB",
      "url": "https://gist.github.com/b-c-ds/b1a2cc0c68a35c57188575eb496de5ce"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/pygments/pygments"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pygments/PYSEC-2021-141.yaml"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2021/03/msg00024.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2021/05/msg00003.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2021/05/msg00006.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GSJRFHALQ7E3UV4FFMFU2YQ6LUDHAI55"
    },
    {
      "type": "WEB",
      "url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WSLD67LFGXOX2K5YNESSWAS4AGZIJTUQ"
    },
    {
      "type": "WEB",
      "url": "https://www.debian.org/security/2021/dsa-4878"
    },
    {
      "type": "WEB",
      "url": "https://www.debian.org/security/2021/dsa-4889"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Pygments vulnerable to Regular Expression Denial of Service (ReDoS)",
  "upstream": [
    "GHSA-pq64-v7f5-gqh8",
    "CVE-2021-27291",
    "PYSEC-2021-141"
  ]
}



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