XSS in Htmlsanitizer Project
CVE-2026-25543
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.004 (26.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 27th percentile — 26.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.001
Affected products
- Htmlsanitizer Project
- Mganss Htmlsanitizer — versions < 9.0.892, < 9.1.893-beta
Weakness classification (CWE)
References
- github.com/mganss/HtmlSanitizer/security/advisories/GHSA-j92c-7v7g-gj3f (Patch, Mitigation, Vendor Advisory)
- github.com/mganss/HtmlSanitizer/commit/0ac53dca30ddad963f2b243669a5066933d82b81 (Patch)
- www.nuget.org/packages/HtmlSanitizer/9.0.892 (Product, Release Notes)
- www.nuget.org/packages/HtmlSanitizer/9.1.893-beta (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-25543?
- CVE-2026-25543 is a medium-severity vulnerability in Htmlsanitizer Project, classified under Improper Encoding or Escaping of Output. CVSS score: 6.1/10. Published 2026-02-04.
- How severe is CVE-2026-25543?
- Medium severity. CVSS v3 base score is 6.1 out of 10.