markdown-it: Quadratic-time denial of service in inline HTML parsing with html enabled

{
  "id": "bae374dfb262150f475125d2873b8f80e8d3c23a2eb61771838352d834764037",
  "url": "https://osv.dev/vulnerability/CVE-2026-111766",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "markdown-it: Quadratic-time denial of service in inline HTML parsing with html enabled",
    "summary": "markdown-it is a Markdown parser. Prior to 14.3.3 and 15.0.3, when the html option or commonmark preset is enabled and the constructs occur inside a paragraph, attacker-controlled Markdown containing repeated unterminated inline HTML comments, processing instructions, declarations, or CDATA sections reaches src/rules_inline/html_inline.ts. Its HTML_TAG_RE match searches the remaining suffix for the appropriate terminator; when no terminator is present, parsing advances to the next opener and repeats the match over overlapping input, causing quadratic processing and denial of service through event-loop blocking or an unresponsive browser main thread. HTML blocks and the default HTML-disabled configuration are not affected by these payloads. This issue is fixed in versions 14.3.3 and 15.0.3.",
    "evidence": "osv:CVE-2026-111766",
    "products": [],
    "severity": "low",
    "structured": {
      "id": "CVE-2026-111766",
      "aliases": [
        "CVE-2026-111766",
        "GHSA-vfgh-jcmw-g37q"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/markdown-it/markdown-it",
              "type": "GIT",
              "events": [
                {
                  "introduced": "157b33bc13649aebecf9ab9b3b8c85ae645abb5a"
                },
                {
                  "fixed": "a8c00d474ec9b304fad9b71c16d6fa8b4909279e"
                },
                {
                  "introduced": "0"
                },
                {
                  "fixed": "d372f0d8a68bef0b0acaa68868ce8ae8ba85b384"
                },
                {
                  "fixed": "928bc8c11ded60181c0e7fc5aa954eec582e8e79"
                },
                {
                  "fixed": "d99f48839d37af6fd8a2617516c43dab90755503"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "15.0.0"
                      },
                      {
                        "fixed": "15.0.3"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "14.3.3"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "928bc8c11ded60181c0e7fc5aa954eec582e8e79"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "d99f48839d37af6fd8a2617516c43dab90755503"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "d372f0d8a68bef0b0acaa68868ce8ae8ba85b384"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "14.3.3"
                  },
                  {
                    "range": [
                      {
                        "fixed": "a8c00d474ec9b304fad9b71c16d6fa8b4909279e"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "15.0.3"
                  }
                ]
              }
            }
          ],
          "versions": [
            "14.3.2",
            "15.0.2",
            "14.3.1",
            "15.0.1",
            "15.0.0",
            "14.3.0",
            "14.2.0",
            "14.1.1",
            "14.1.0",
            "14.0.0",
            "13.0.2",
            "13.0.1",
            "13.0.0",
            "12.3.2",
            "12.3.1",
            "12.3.0",
            "12.2.0",
            "12.1.0",
            "12.0.6",
            "12.0.5",
            "12.0.4",
            "12.0.3",
            "12.0.2",
            "12.0.1",
            "12.0.0",
            "11.0.1",
            "11.0.0",
            "10.0.0",
            "9.1.0",
            "9.0.1",
            "9.0.0",
            "8.4.2",
            "8.4.1",
            "8.4.0",
            "8.3.2",
            "8.3.1",
            "8.3.0",
            "8.2.2",
            "8.2.1",
            "8.2.0",
            "8.1.0",
            "8.0.1",
            "8.0.0",
            "7.0.1",
            "7.0.0",
            "6.1.1",
            "6.1.0",
            "6.0.5",
            "6.0.4",
            "6.0.3",
            "6.0.2",
            "6.0.1",
            "6.0.0",
            "5.1.0",
            "5.0.3",
            "5.0.2",
            "5.0.1",
            "5.0.0",
            "4.4.0",
            "4.3.1",
            "4.3.0",
            "4.2.2",
            "4.2.1",
            "4.2.0",
            "4.1.2",
            "4.1.1",
            "4.1.0",
            "4.0.3",
            "4.0.2",
            "4.0.1",
            "4.0.0",
            "3.1.0",
            "3.0.7",
            "3.0.6",
            "3.0.5",
            "3.0.4",
            "3.0.3",
            "3.0.2",
            "3.0.1",
            "3.0.0",
            "2.2.1",
            "2.2.0",
            "2.1.3",
            "2.1.2",
            "2.1.1",
            "2.1.0",
            "2.0.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-111766.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:46.225281131Z",
      "provider": "osv",
      "references": [
        "https://github.com/markdown-it/markdown-it/releases/tag/14.3.3",
        "https://github.com/markdown-it/markdown-it/releases/tag/15.0.3",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/111xxx/CVE-2026-111766.json",
        "https://github.com/markdown-it/markdown-it/security/advisories/GHSA-vfgh-jcmw-g37q",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-111766",
        "https://github.com/markdown-it/markdown-it/commit/928bc8c11ded60181c0e7fc5aa954eec582e8e79",
        "https://github.com/markdown-it/markdown-it/commit/d99f48839d37af6fd8a2617516c43dab90755503"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-400",
          "CWE-407"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/111xxx/CVE-2026-111766.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-111766",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 514399,
  "published_at": "2026-10-19T19:47:46.488+00:00"
}