GHSA-58CW-G322-P94V

Vulnerability from github – Published: 2026-05-08 23:43 – Updated: 2026-06-08 23:34
VLAI
Summary
Mistune has XSS via unescaped figclass/figwidth in Figure directive
Details

In src/mistune/directives/image.py, the render_figure() function concatenates figclass and figwidth options directly into HTML attributes without escaping (lines 152-168).

This allows attribute injection and XSS even when HTMLRenderer(escape=True) is used, because these values bypass the inline renderer.

Other attributes in the same file (src, alt, style) are properly escaped; figclass/figwidth were missed.

Severity
6.1 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
5.3 (Medium)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.2.0"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "mistune"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44896"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-08T23:43:12Z",
    "nvd_published_at": "2026-05-26T21:16:39Z",
    "severity": "MODERATE"
  },
  "details": "In `src/mistune/directives/image.py`, the `render_figure()` function concatenates `figclass` and `figwidth` options directly into HTML attributes without escaping (lines 152-168).\n\nThis allows attribute injection and XSS even when `HTMLRenderer(escape=True)` is used, because these values bypass the inline renderer.\n\nOther attributes in the same file (src, alt, style) are properly escaped; figclass/figwidth were missed.",
  "id": "GHSA-58cw-g322-p94v",
  "modified": "2026-06-08T23:34:18Z",
  "published": "2026-05-08T23:43:12Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-58cw-g322-p94v"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44896"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/commit/a3cb6e5655308797e8be021d6c7b5bab13cbace2"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lepture/mistune"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-168.yaml"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Mistune has XSS via unescaped figclass/figwidth in Figure directive"
}



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