CVE-2026-25543

HtmlSanitizer has a bypass via template tag

CVSS 6.3 MEDIUMEPSS 0.2%CWE-116

Vexday Risk Score

13Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 6.3EPSS 0.2%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

04 Feb 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

HtmlSanitizer is a .NET library for cleaning HTML fragments and documents from constructs that can lead to XSS attacks. Prior to versions 9.0.892 and 9.1.893-beta, if the template tag is allowed, its contents are not sanitized. The template tag is a special tag that does not usually render its contents, unless the shadowrootmode attribute is set to open or closed. This issue has been patched in versions 9.0.892 and 9.1.893-beta.

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Affected products

mganss · HtmlSanitizer

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References

https://github.com/mganss/HtmlSanitizer/commit/0ac53dca30ddad963f2b243669a5066933d82b81 https://github.com/mganss/HtmlSanitizer/security/advisories/GHSA-j92c-7v7g-gj3f https://www.nuget.org/packages/HtmlSanitizer/9.0.892 https://www.nuget.org/packages/HtmlSanitizer/9.1.893-beta