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CVE-2026-5751

MediumCVSS 5.1 / 10
Published Aug 23, 2026·Last modified Aug 24, 2026
Affected Components(58)
emilstenstrom/justhtml
0.5.0
emilstenstrom/justhtml
0.1.0
emilstenstrom/justhtml
0.13.0
1 / 20
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.

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Risk Scores
Base Score
5.1

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights.

Threat Intelligence
1.2

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
0.19%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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