FKIE_CVE-2026-44898

Vulnerability from fkie_nvd - Published: 2026-05-26 21:16 - Updated: 2026-05-28 13:42
Severity
6.1 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Summary
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_toc_ul() builds a <ul> table-of-contents tree from a list of (level, id, text) tuples. Both the id value (used as href="#<id>") and the text value (used as the visible link label) are inserted into <a> 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 <script> blocks directly into the rendered TOC. This vulnerability is fixed in 3.2.1.
References
security-advisories@github.comhttps://github.com/lepture/mistune/releases/tag/v3.2.1Product, Release Notes
security-advisories@github.comhttps://github.com/lepture/mistune/security/advisories/GHSA-6269-cqxg-mhhvExploit, Vendor Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0https://github.com/lepture/mistune/security/advisories/GHSA-6269-cqxg-mhhvExploit, Vendor Advisory
Impacted products
Vendor Product Version
mistune_project mistune *
To clipboard 

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "A91629D7-7A30-4A3F-B1AD-17FE21D59820",
              "versionEndExcluding": "3.2.1",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_toc_ul() builds a \u003cul\u003e table-of-contents tree from a list of (level, id, text) tuples. Both the id value (used as href=\"#\u003cid\u003e\") and the text value (used as the visible link label) are inserted into \u003ca\u003e tags via a plain Python format string \u2014 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 \u003cscript\u003e blocks directly into the rendered TOC. This vulnerability is fixed in 3.2.1."
    }
  ],
  "id": "CVE-2026-44898",
  "lastModified": "2026-05-28T13:42:13.527",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 6.1,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 2.7,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-05-26T21:16:39.810",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Product",
        "Release Notes"
      ],
      "url": "https://github.com/lepture/mistune/releases/tag/v3.2.1"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-6269-cqxg-mhhv"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-6269-cqxg-mhhv"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}


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