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Vulnerability Intelligence

Vulnerability IntelligenceCVE-2026-25543

CVE-2026-25543

MEDIUM6.3

HtmlSanitizer has a bypass via template tag

Published Feb 4, 2026

Modified 3 weeks ago

Details

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.

References

https://github.com/mganss/HtmlSanitizer/commit/0ac53dca30ddad963f2b243669a5066933d82b81

https://github.com/mganss/HtmlSanitizer/security/advisories/GHSA-j92c-7v7g-gj3f

https://www.cve.org/CVERecord?id=CVE-2026-25543

https://www.nuget.org/packages/HtmlSanitizer/9.0.892

https://www.nuget.org/packages/HtmlSanitizer/9.1.893-beta

CVSS Analysis

CVSS v4.0

6.3

Exploitability

Attack Vector

NetworkAV:N

Attack Complexity

LowAC:L

Attack Requirements

PresentAT:P

Privileges Required

NonePR:N

User Interaction

NoneUI:N

Vulnerable System

Vuln. Confidentiality

NoneVC:N

Vuln. Integrity

NoneVI:N

Vuln. Availability

NoneVA:N

Subsequent System

Subseq. Confidentiality

LowSC:L

Subseq. Integrity

LowSI:L

Subseq. Availability

NoneSA:N

6.3/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

Weakness Type (CWE)

Input Validation

Improper Encoding/Escaping

Ecosystems

Timeline

PublishedFeb 4, 2026

ModifiedFeb 5, 2026

CVE-2026-25543 | Mondoo Vulnerability Intelligence