{"id":"CVE-2026-6827","title":"justhtml before 1.17.0 contains multiple security issues in sanitization, serialization, and programmatic DOM handling","summary":"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…","severity":"medium","cvss":6.1,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","cwe":["CWE-79"],"vendor":"justhtml","product":"justhtml","affected":["justhtml < 1.17.0"],"patched":["justhtml 1.17.0"],"published":"2026-08-23","updated":"2026-10-12","sourceUpdated":"2026-10-12T16:10:00.220","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-6827","references":[{"url":"https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-vrx2-77f2-ww34","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/justhtml-before-multiple-cross-site-scripting-vulnerabilities","label":"disclosure@vulncheck.com"},{"url":"https://github.com/EmilStenstrom/justhtml"}],"tags":["nvd","osv","pip"],"epss":0.00261,"epssPercentile":0.17801,"aliases":["GHSA-vrx2-77f2-ww34"],"ecosystem":"pip","ingestedAt":"2026-08-24T19:25:44.456Z","slug":"CVE-2026-6827","body":"## Overview\n\njusthtml 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-6827)\n\nAffected packages:\n\n- `justhtml < 1.17.0`\n\nPatched in:\n\n- `justhtml 1.17.0`\n\nSource: https://osv.dev/vulnerability/GHSA-vrx2-77f2-ww34","depth":"sunlit","depthScore":34,"depthScoreParts":{"impact":33.6,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":219487,"id":"CVE-2026-6827","ts":1791824360623,"field":"cvss","old":null,"new":"6.1"}]}