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CVE-2026-6827

MediumCVSS 5.1 / 10
Published Aug 23, 2026·Last modified Aug 24, 2026
Affected Components(61)
emilstenstrom/justhtml
0.5.0
emilstenstrom/justhtml
0.1.0
emilstenstrom/justhtml
0.13.0
1 / 21
Description

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.

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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
0.26%

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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