CVE-2026-5751

MediumCVSS 6.1/10Last modified Oct 12, 2026

Description

justhtml versions 1.13.0 and earlier contain a parser-differential / mutation cross-site scripting (mXSS) vulnerability when using a custom SanitizationPolicy that preserves foreign namespaces (e.g., drop_foreign_namespaces=False with allowlisted SVG/MathML elements or raw-text containers such as <style>). Specially crafted input can sanitize into markup that appears safe but becomes unsafe when re-parsed by a browser or another HTML parser, allowing markup injection. The default safe configuration (sanitize=True) is not affected. Fixed in 1.14.0.

Metrics

CVSS 3.1 6.1/10CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Weakness enumeration

Affected software

No affected versions have been published.

Timeline

Published
Aug 23, 2026
Last modified
Oct 12, 2026
NVD status
Deferred

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CVE-2026-5751: Medium severity, CVSS 6.1 | Vulnix