CVE WatchAug 23, 2026

CVE-2026-5751

justhtml versions 1.13.0 and earlier contain a parser-differential / mutation cross-site scripting (mXSS) vulnerability when using a custom

CVSS

6.1

Medium

EPSS

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KEV

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Exploit Today

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0-100

Published: Aug 23, 2026 · Last modified: Aug 23, 2026 · CWE-79

EPSS · 30d

Not enough EPSS history yet.

Technical 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.

Official references

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