GHSA-5239-WWWM-4PMQ

Vulnerability from github – Published: 2026-03-22 06:30 – Updated: 2026-03-30 14:40
VLAI
Summary
Pygments has Regular Expression Denial of Service (ReDoS) due to Inefficient Regex for GUID Matching
Details

A security flaw has been discovered in pygments before 2.20.0. The impacted element is the function AdlLexer of the file pygments/lexers/archetype.py. The manipulation results in inefficient regular expression complexity. The attack is only possible with local access. The exploit has been released to the public and may be used for attacks. The project was informed of the problem early through an issue report but has not responded yet.

Severity
3.3 (Low)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
1.9 (Low)
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "Pygments"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.20.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-4539"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333",
      "CWE-400"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-24T20:33:39Z",
    "nvd_published_at": "2026-03-22T06:16:20Z",
    "severity": "LOW"
  },
  "details": "A security flaw has been discovered in pygments before 2.20.0. The impacted element is the function AdlLexer of the file pygments/lexers/archetype.py. The manipulation results in inefficient regular expression complexity. The attack is only possible with local access. The exploit has been released to the public and may be used for attacks. The project was informed of the problem early through an issue report but has not responded yet.",
  "id": "GHSA-5239-wwwm-4pmq",
  "modified": "2026-03-30T14:40:28Z",
  "published": "2026-03-22T06:30:15Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-4539"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pygments/pygments/issues/3058"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pygments/pygments/pull/3064"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pygments/pygments/commit/24b8aa76c6cd6d70f39c6dd605cce319c98e2ccc"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/pygments/pygments"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pygments/pygments/releases/tag/2.20.0"
    },
    {
      "type": "WEB",
      "url": "https://vuldb.com/?ctiid.352327"
    },
    {
      "type": "WEB",
      "url": "https://vuldb.com/?id.352327"
    },
    {
      "type": "WEB",
      "url": "https://vuldb.com/?submit.774685"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Pygments has Regular Expression Denial of Service (ReDoS) due to Inefficient Regex for GUID Matching"
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.