CVE-2026-111766 (GCVE-0-2026-111766)

Vulnerability from cvelistv5 – Published: 2026-10-19 19:47 – Updated: 2026-10-19 19:47
VLAI
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.
Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
CWE
  • CWE-400 - Uncontrolled Resource Consumption
  • CWE-407 - Inefficient Algorithmic Complexity
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7613 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
markdown-it markdown-it Affected: >= 15.0.0, < 15.0.3
Affected: < 14.3.3
guessed Create a notification for this product.
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "markdown-it",
          "vendor": "markdown-it",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 15.0.0, \u003c 15.0.3"
            },
            {
              "status": "affected",
              "version": "\u003c 14.3.3"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 3.7,
            "baseSeverity": "LOW",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-400",
              "description": "CWE-400: Uncontrolled Resource Consumption",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-407",
              "description": "CWE-407: Inefficient Algorithmic Complexity",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T19:47:46.488Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/markdown-it/markdown-it/security/advisories/GHSA-vfgh-jcmw-g37q",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/markdown-it/markdown-it/security/advisories/GHSA-vfgh-jcmw-g37q"
        },
        {
          "name": "https://github.com/markdown-it/markdown-it/commit/928bc8c11ded60181c0e7fc5aa954eec582e8e79",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/markdown-it/markdown-it/commit/928bc8c11ded60181c0e7fc5aa954eec582e8e79"
        },
        {
          "name": "https://github.com/markdown-it/markdown-it/commit/d99f48839d37af6fd8a2617516c43dab90755503",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/markdown-it/markdown-it/commit/d99f48839d37af6fd8a2617516c43dab90755503"
        },
        {
          "name": "https://github.com/markdown-it/markdown-it/releases/tag/14.3.3",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/markdown-it/markdown-it/releases/tag/14.3.3"
        },
        {
          "name": "https://github.com/markdown-it/markdown-it/releases/tag/15.0.3",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/markdown-it/markdown-it/releases/tag/15.0.3"
        }
      ],
      "source": {
        "advisory": "GHSA-vfgh-jcmw-g37q",
        "discovery": "UNKNOWN"
      },
      "title": "markdown-it: Quadratic-time denial of service in inline HTML parsing with html enabled"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-111766",
    "datePublished": "2026-10-19T19:47:46.488Z",
    "dateReserved": "2026-10-16T17:52:09.082Z",
    "dateUpdated": "2026-10-19T19:47:46.488Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "product": "markdown-it",
                "vendor": "markdown-it",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003e= 15.0.0, \u003c 15.0.3"
                  },
                  {
                    "status": "affected",
                    "version": "\u003c 14.3.3"
                  }
                ]
              }
            ],
            "source": "security-advisories@github.com"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "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."
          }
        ],
        "id": "CVE-2026-111766",
        "lastModified": "2026-10-19T21:13:39.973",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "HIGH",
                "attackVector": "NETWORK",
                "availabilityImpact": "LOW",
                "baseScore": 3.7,
                "baseSeverity": "LOW",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
                "version": "3.1"
              },
              "exploitabilityScore": 2.2,
              "impactScore": 1.4,
              "source": "security-advisories@github.com",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-10-19T20:17:52.247",
        "references": [
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/markdown-it/markdown-it/commit/928bc8c11ded60181c0e7fc5aa954eec582e8e79"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/markdown-it/markdown-it/commit/d99f48839d37af6fd8a2617516c43dab90755503"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/markdown-it/markdown-it/releases/tag/14.3.3"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/markdown-it/markdown-it/releases/tag/15.0.3"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/markdown-it/markdown-it/security/advisories/GHSA-vfgh-jcmw-g37q"
          }
        ],
        "sourceIdentifier": "security-advisories@github.com",
        "vulnStatus": "Awaiting Analysis",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-400"
              },
              {
                "lang": "en",
                "value": "CWE-407"
              }
            ],
            "source": "security-advisories@github.com",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-10-19T23:47:59+00:00",
      "cve": "CVE-2026-111766",
      "id": "CVE-2026-111766",
      "initial_release_date": "2026-10-19T19:47:46.488000+00:00",
      "product_status:known_affected": "14",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "markdown-it: markdown-it: Denial of Service via repeated unterminated inline HTML constructs",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-111766.json",
      "version": "3"
    }
  }
}



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