{"id":"CVE-2026-6827","aliases":["GHSA-vrx2-77f2-ww34"],"url":"https://o3.security/vulnerability/CVE-2026-6827","summary":"justhtml before 1.17.0 Multiple Cross-Site Scripting Vulnerabilities","details":"justhtml before 1.17.0 contains multiple security issues in sanitization, serialization, and programmatic DOM handling. When custom policies preserve foreign namespaces (SVG/MathML), dangerous content such as HTML integration points (SVG <foreignObject>, MathML <annotation-xml encoding=\"text/html\">) and mutation-XSS parser-differential payloads could survive sanitization and become active HTML after reparse; SVG filter=\"url(...)\" and preserved <style> could leave resource-loading CSS (@import, background-image:url()). Programmatic script/style/Comment nodes could serialize into active markup. Additional hardening fixes address sanitize-pipeline cache mutation and DOM parent/child cycles that could cause infinite loops. Most issues affect advanced or custom configurations rather than the default JustHTML(..., sanitize=True) safe path.","published":"2026-08-23T13:34:11.236Z","modified":"2026-08-27T03:30:51.287072127Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"PyPI","name":"justhtml","fixedVersion":"1.17.0"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/6xxx/CVE-2026-6827.json"},{"type":"ADVISORY","url":"https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-vrx2-77f2-ww34"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-6827"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/justhtml-before-multiple-cross-site-scripting-vulnerabilities"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-27T03:30:51.287072127Z"}}