CVE catalog

CVE-2026-59928

Mistune is a Python Markdown parser with renderers and…

[CVE catalog]

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/block_parser.py and the ref_links environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.

Severity
High · CVSS 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
Source
[NVD] · [CVE record]
EPSS
0.65% · Oct 27, 2026

Projects and upstream resources

Reported versions and fixes

Each observation applies to its named package, distribution, and release. Distribution backports can fix a vulnerability while retaining an older upstream version number.

Version impact has not been established. The original provider fields are retained below.

Provider details and historical evidence
Original provider fields
{
  "package_releases": [
    {
      "name": "mistune",
      "status": "fixed",
      "release": "sid",
      "version": "3.4.0-1"
    },
    {
      "name": "mistune",
      "status": "vulnerable",
      "release": "forky",
      "version": "3.1.4-1"
    },
    {
      "name": "mistune",
      "status": "vulnerable",
      "release": "trixie",
      "version": "3.1.3-1"
    },
    {
      "name": "mistune",
      "status": "not affected",
      "release": "bookworm",
      "version": "2.0.4-1"
    }
  ],
  "fixed_versions": [
    {
      "bug": 1141770,
      "name": "mistune",
      "type": "source",
      "origin": null,
      "release": "sid",
      "urgency": "not yet assigned",
      "fixed_version": "3.3.4-1"
    },
    {
      "bug": 1141770,
      "name": "mistune",
      "type": "source",
      "origin": null,
      "release": "forky",
      "urgency": "not yet assigned",
      "fixed_version": ""
    },
    {
      "bug": 1141770,
      "name": "mistune",
      "type": "source",
      "origin": null,
      "release": "trixie",
      "urgency": "not yet assigned",
      "fixed_version": ""
    },
    {
      "bug": 1141770,
      "name": "mistune",
      "type": "source",
      "origin": null,
      "release": "bookworm",
      "urgency": "unimportant",
      "fixed_version": "0"
    }
  ],
  "distribution_packages": [
    {
      "name": "mistune",
      "ecosystem": "cpe",
      "fixed_version": "3.3.0"
    },
    {
      "name": "mistune",
      "ecosystem": "pip",
      "fixed_version": "3.3.0"
    },
    {
      "name": "mistune",
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.3.0"
            }
          ]
        }
      ],
      "ecosystem": "PyPI",
      "fixed_version": "3.3.0"
    },
    {
      "name": "mistune",
      "ranges": [
        {
          "fixed": "3.3.0",
          "introduced": "",
          "last_affected": "",
          "start_excluding": ""
        }
      ],
      "ecosystem": "cpe",
      "fixed_version": "3.3.0",
      "provider_record_id": "NVD-CVE-2026-59928"
    }
  ]
}

[Debian bug #1141770]

Publisher notes

[trixie] mistune: Minor issue

OpenFactory catalog packages

Matching against OpenFactory catalog package versions is in progress.

[Debian 12 (Bookworm)]

  • [python3-mistune]Unknown

    Source package: [mistune]

    Details (2)

    • 2.0.4-1 · all · bookworm

      Not affected

      nvd · mistune · debian · bookworm

    • 2.0.4-1 · all · bookworm

      Not affected

      nvd · mistune · debian · bookworm

[Debian 13 (Trixie)]

  • [python3-mistune]Unknown

    Source package: [mistune]

    Details (2)

    • 3.1.3-1 · all · trixie

      Affected

      nvd · mistune · debian · 13

    • 3.1.3-1 · all · trixie

      Affected

      nvd · mistune · debian · 13

Observed:

References

[Debian Security Tracker] · [FIRST EPSS] · [GitHub Advisory Database] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]