{
"id": "GHSA-g97x-gvcm-x72h",
"aliases": [
"CVE-2026-59926"
],
"details": "In `src/mistune/directives/admonition.py`, the `render_admonition()` function concatenates the `:class:` option directly into the HTML class attribute without escaping (lines 63-68).\n\nThis allows attribute injection and XSS even when `HTMLRenderer(escape=True)` is used.\n\nThe directive name parameter is safe (validated against whitelist), but the class option comes from raw user input.",
"summary": "Mistune: XSS via unescaped class option in Admonition directive",
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "3.3.0"
}
]
}
],
"package": {
"name": "mistune",
"ecosystem": "PyPI"
}
}
],
"modified": "2026-07-20T21:34:14Z",
"severity": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N"
}
],
"published": "2026-07-20T21:34:14Z",
"references": [
{
"url": "https://github.com/lepture/mistune/security/advisories/GHSA-g97x-gvcm-x72h",
"type": "WEB"
},
{
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59926",
"type": "ADVISORY"
},
{
"url": "https://github.com/lepture/mistune/commit/a3cb6e5655308797e8be021d6c7b5bab13cbace2",
"type": "WEB"
},
{
"url": "https://github.com/lepture/mistune",
"type": "PACKAGE"
},
{
"url": "https://github.com/lepture/mistune/releases/tag/v3.2.1",
"type": "WEB"
},
{
"url": "https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2214.yaml",
"type": "WEB"
}
],
"schema_version": "1.4.0",
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"severity": "MODERATE",
"github_reviewed": true,
"nvd_published_at": "2026-07-08T17:17:28Z",
"github_reviewed_at": "2026-07-20T21:34:14Z"
}
}