CVE-2026-5751: medium-severity vulnerability in EmilStenstrom justhtml
justhtml before 1.14.0 Mutation XSS via custom sanitization policies
Published · Updated
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13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.1epss 0.3%
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.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Affected products
EmilStenstrom · justhtmlRelated CVEs — EmilStenstrom justhtml
In the same product, most dangerous first.
CVE-2026-4671HIGHjusthtml before 1.18.0 Denial of Service via CSS SelectorEPSS 0.7%CVE-2026-8445CRITICALjusthtml before 1.12.0 Sanitizer Bypass via MarkdownEPSS 0.6%CVE-2026-7808CRITICALjusthtml before 1.16.0 Multiple Security Issues via SanitizationEPSS 0.6%CVE-2026-5388CRITICALjusthtml before 1.15.0 Multiple Security IssuesEPSS 0.6%CVE-2026-9769HIGHjusthtml before 1.10.0 Denial of Service via deeply nested HTMLEPSS 0.3%CVE-2026-8630MEDIUMjusthtml before 1.12.0 Mutation XSS via Raw Text ElementsEPSS 0.3%