mistune — security advisory

{
  "id": "fb3cc91a9dc9ec8b45dfe41f7edcdcd16aa1f8dbbc2fd20b06af28c663f53978",
  "url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-59926",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "DEBIAN-CVE-2026-59926",
    "summary": "Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_admonition() in src/mistune/directives/admonition.py concatenates the Admonition directive :class: option into the HTML class attribute without escaping, allowing attribute injection and cross-site scripting even when HTMLRenderer escape mode is enabled. This issue is fixed in version 3.2.1.",
    "evidence": "osv:DEBIAN-CVE-2026-59926",
    "products": [
      {
        "name": {
          "value": "mistune",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "3.1.3-1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "3.1.4-1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "3.3.4-1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "3.4.0-1",
            "evidence": "/affected/0/versions"
          }
        ]
      },
      {
        "name": {
          "value": "mistune",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "3.1.4-1",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "3.1.3-1",
            "evidence": "/affected/1/versions"
          }
        ]
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "DEBIAN-CVE-2026-59926",
      "aliases": [
        "DEBIAN-CVE-2026-59926"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "mistune",
            "purl": "pkg:deb/debian/mistune?arch=source&distro=trixie",
            "ecosystem": "Debian:13"
          },
          "versions": [
            "3.1.3-1",
            "3.1.4-1",
            "3.3.4-1",
            "3.4.0-1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-59926.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "3.1.4-1"
                }
              ]
            }
          ],
          "package": {
            "name": "mistune",
            "purl": "pkg:deb/debian/mistune?arch=source&distro=forky",
            "ecosystem": "Debian:14"
          },
          "versions": [
            "3.1.3-1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-59926.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        }
      ],
      "modified": "2026-10-26T11:47:24.567988734Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-59926"
      ],
      "references": [
        "https://security-tracker.debian.org/tracker/CVE-2026-59926"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-59926",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 450841,
  "published_at": "2026-07-08T17:17:28.323+00:00"
}