CVE-2026-54570
AngleSharp: HTML5 Spec Compliance: mXSS via annotation-xml HTML Integration Point Bypass
- State
- Published
- Severity
- 6.9 Medium
- Published
- Aug 18, 2026
- Updated
- Aug 18, 2026
- Reserved
- Jun 15, 2026
Description
AngleSharp is a .NET library for parsing angle bracket based hyper-texts. Prior to 1.5.0, MathAnnotationXmlElement in AngleSharp/Mathml/Dom/Internal/MathAnnotationXmlElement.cs is not treated as an HTML integration point when its encoding attribute is text/html or application/xhtml+xml, causing Consume in AngleSharp/Html/Parser/HtmlDomBuilder.cs to route tokens through foreign-content parsing instead of HTML parsing. A sanitizer can therefore observe a different DOM from the browser that reparses the serialized output. An attacker can combine this namespace differential with markup-breaking characters in an attribute value so that an element hidden from the sanitizer becomes active script-capable HTML after browser reparse, resulting in mutation cross-site scripting. This issue is fixed in version 1.5.0.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 6.9 Medium | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:N | GitHub_M |
Weaknesses
- CWE-80 Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)
Affected Products
| Product | Versions |
|---|---|
AngleSharpAngleSharp |
|
References
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