CVE-2026-6827 (GCVE-0-2026-6827)
Vulnerability from cvelistv5 – Published: 2026-08-23 13:34 – Updated: 2026-08-29 11:47
VLAI
EPSS
VEX
Title
justhtml before 1.17.0 Multiple Cross-Site Scripting Vulnerabilities
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 <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.
Severity
6.1 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-26 18:05 UTC
CWE
- CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Assigner
VulnCheck
CNA
References
2 references
| URL | Tags |
|---|---|
| https://github.com/EmilStenstrom/justhtml/securit… | vendor-advisory |
| https://www.vulncheck.com/advisories/justhtml-bef… | third-party-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| EmilStenstrom | justhtml |
Affected:
0 , < 1.17.0
(semver)
Unaffected: 1.17.0 (semver) |
Date Public
2026-04-19 00:00
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