Mistune TOC Anchor Injection XSS

{
  "id": "3e3591a62c961d1e85eab0b99eef7692a67a1b143d1a685a4155f10e0e822746",
  "url": "https://osv.dev/vulnerability/CVE-2026-44898",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Mistune TOC Anchor Injection XSS",
    "summary": "Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_toc_ul() builds a table-of-contents tree from a list of (level, id, text) tuples. Both the id value (used as href=\"#\") and the text value (used as the visible link label) are inserted into tags via a plain Python format string — with no HTML escaping applied to either value. When heading IDs are derived from user-supplied heading text (the standard use-case for readable slug anchors), an attacker can craft a heading whose text breaks out of the href=\"#...\" attribute context, injecting arbitrary HTML tags including",
    "evidence": "osv:CVE-2026-44898",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-44898",
      "aliases": [
        "CVE-2026-44898",
        "GHSA-6269-cqxg-mhhv",
        "PYSEC-2026-2208"
      ],
      "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": [
            {
              "repo": "https://github.com/lepture/mistune",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "067f90861088a496942f5eb43236135352b85d39"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "3.2.1"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "067f90861088a496942f5eb43236135352b85d39"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v3.2.1"
                  },
                  {
                    "cpe": "cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "3.2.1"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v3.2.0",
            "v3.1.4",
            "v3.1.3",
            "v3.1.2",
            "v3.1.1",
            "v3.1.0",
            "v3.0.1",
            "v3.0.0",
            "v3.0.0rc5",
            "v3.0.0rc4",
            "v3.0.0rc3",
            "v3.0.0rc2",
            "v3.0.0rc1",
            "v3.0.0a3",
            "v3.0.0a2",
            "v3.0.0a1",
            "v2.0.2",
            "v2.0.1",
            "v2.0.0",
            "v2.0.0rc1",
            "v2.0.0a6",
            "v2.0.0a5",
            "v2.0.0a4",
            "v2.0.0a3",
            "v2.0.0a2",
            "v2.0.0a1",
            "v0.8.4",
            "v0.8.3",
            "v0.8.2",
            "v0.8.1",
            "v0.8",
            "v0.7.4",
            "v0.7.3",
            "v0.7.2",
            "v0.7.1",
            "v0.7",
            "v0.6",
            "v0.5.1",
            "v0.5",
            "v0.4.1",
            "v0.4",
            "v0.3.1",
            "v0.3.0",
            "v0.2.0",
            "v0.1.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-44898.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:51.123510733Z",
      "provider": "osv",
      "references": [
        "https://github.com/lepture/mistune/releases/tag/v3.2.1",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44898.json",
        "https://github.com/lepture/mistune/security/advisories/GHSA-6269-cqxg-mhhv",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-44898"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-79"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44898.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-44898",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 519838,
  "published_at": "2026-05-26T20:41:53.805+00:00"
}