CVE-2026-54570
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.
Does this matter?
Lower severity and a low EPSS score (0.25%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 6.9 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:N
- EPSS
- 0.25% probability · 16th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-80
- Source
- security-advisories@github.com
References
- https://github.com/AngleSharp/AngleSharp/commit/8033a5c690af9c2c443f58e34875343fa4cc1d07
- https://github.com/AngleSharp/AngleSharp/releases/tag/1.5.0
- https://github.com/AngleSharp/AngleSharp/security/advisories/GHSA-pgww-w46g-26qg
- https://github.com/AngleSharp/AngleSharp/security/advisories/GHSA-pgww-w46g-26qg
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.