HighFix available

pymdown-extensions — security advisory

Type: advisorySources: OSVAdvisory ID: DEBIAN-CVE-2026-67422

pymdown-extensions is a collection of extensions for the Python Markdown library. In versions up to and including 11.0, four inline processors (caret, tilde, betterem, and magiclink) use regular expressions whose content groups can partition a run of delimiter characters in exponentially many ways, causing catastrophic backtracking. As a result, a single untrusted Markdown line under 50 bytes rendered with markdown.markdown() in each extension's default configuration drives the rendering thread into unbounded CPU usage that grows exponentially with input length, enabling an unauthenticated remote attacker who can submit Markdown to cause denial of service. The exposure is concrete for web applications that render user-supplied Markdown (comments, wikis, issue bodies, live preview), including any app using pymdownx.extra which bundles the vulnerable betterem default, as well as hosted docs/CI systems that build untrusted Markdown. The issue has been fixed in version 11.0.1.

Products: pymdown-extensions
Affected versions: 10.11.2-1, 10.13-1, 10.13-1+deb13u1, 10.13-2, 10.13-3, 10.13-4, 10.19.1-1, 10.19.1-3, 10.8.1-1, 10.9-1, 11.0.1-1, 9.5-2, 9.5-3, 9.5-4, 9.5-5
Fixed versions: 11.0.1-1
CVEs: CVE-2026-67422
Confirmed fixed CVEs: Not specified
Updated in this feed: 1 Nov 2026, 09:54 UTC · Revision 1

Source evidence

DEBIAN-CVE-2026-67422

core-osv · Original source

Published 6 Aug 2026, 22:18 UTC

osv:DEBIAN-CVE-2026-67422

pymdown-extensions

Fixed versions: Not specified

pymdown-extensions

Fixed versions: Not specified

pymdown-extensions

Fixed versions: 11.0.1-1

Complete source record

{
  "id": "b066f5656277b3be3c11cf89eeab893dceedb97caf00d56e78aad1f48deaf163",
  "url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-67422",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "DEBIAN-CVE-2026-67422",
    "summary": "pymdown-extensions is a collection of extensions for the Python Markdown library. In versions up to and including 11.0, four inline processors (caret, tilde, betterem, and magiclink) use regular expressions whose content groups can partition a run of delimiter characters in exponentially many ways, causing catastrophic backtracking. As a result, a single untrusted Markdown line under 50 bytes rendered with markdown.markdown() in each extension's default configuration drives the rendering thread into unbounded CPU usage that grows exponentially with input length, enabling an unauthenticated remote attacker who can submit Markdown to cause denial of service. The exposure is concrete for web applications that render user-supplied Markdown (comments, wikis, issue bodies, live preview), including any app using pymdownx.extra which bundles the vulnerable betterem default, as well as hosted docs/CI systems that build untrusted Markdown. The issue has been fixed in version 11.0.1.",
    "evidence": "osv:DEBIAN-CVE-2026-67422",
    "products": [
      {
        "name": {
          "value": "pymdown-extensions",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "10.11.2-1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "10.13-1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "10.13-2",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "10.13-3",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "10.13-4",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "10.19.1-1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "10.19.1-3",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "10.8.1-1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "10.9-1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "11.0.1-1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "9.5-2",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "9.5-3",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "9.5-4",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "9.5-5",
            "evidence": "/affected/0/versions"
          }
        ]
      },
      {
        "name": {
          "value": "pymdown-extensions",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "10.13-1",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "10.13-1+deb13u1",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "10.13-2",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "10.13-3",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "10.13-4",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "10.19.1-1",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "10.19.1-3",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "11.0.1-1",
            "evidence": "/affected/1/versions"
          }
        ]
      },
      {
        "name": {
          "value": "pymdown-extensions",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "11.0.1-1",
            "evidence": "/affected/2/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "10.13-1",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "10.13-2",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "10.13-3",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "10.13-4",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "10.19.1-1",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "10.19.1-3",
            "evidence": "/affected/2/versions"
          }
        ]
      }
    ],
    "severity": "high",
    "structured": {
      "id": "DEBIAN-CVE-2026-67422",
      "aliases": [
        "DEBIAN-CVE-2026-67422"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "pymdown-extensions",
            "purl": "pkg:deb/debian/pymdown-extensions?arch=source&distro=bookworm",
            "ecosystem": "Debian:12"
          },
          "versions": [
            "10.11.2-1",
            "10.13-1",
            "10.13-2",
            "10.13-3",
            "10.13-4",
            "10.19.1-1",
            "10.19.1-3",
            "10.8.1-1",
            "10.9-1",
            "11.0.1-1",
            "9.5-2",
            "9.5-3",
            "9.5-4",
            "9.5-5"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-67422.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "pymdown-extensions",
            "purl": "pkg:deb/debian/pymdown-extensions?arch=source&distro=trixie",
            "ecosystem": "Debian:13"
          },
          "versions": [
            "10.13-1",
            "10.13-1+deb13u1",
            "10.13-2",
            "10.13-3",
            "10.13-4",
            "10.19.1-1",
            "10.19.1-3",
            "11.0.1-1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-67422.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "11.0.1-1"
                }
              ]
            }
          ],
          "package": {
            "name": "pymdown-extensions",
            "purl": "pkg:deb/debian/pymdown-extensions?arch=source&distro=forky",
            "ecosystem": "Debian:14"
          },
          "versions": [
            "10.13-1",
            "10.13-2",
            "10.13-3",
            "10.13-4",
            "10.19.1-1",
            "10.19.1-3"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-67422.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        }
      ],
      "modified": "2026-10-25T09:47:29.606465984Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-67422"
      ],
      "references": [
        "https://security-tracker.debian.org/tracker/CVE-2026-67422"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-67422",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 445244,
  "published_at": "2026-08-06T22:18:21.6+00:00"
}