Vulnerability · Published Aug 18, 2026 · Assigned by GitHub_M
CVE-2026-54570AngleSharp: HTML5 Spec Compliance: mXSS via annotation-xml HTML Integration Point Bypass
Medium 6.9
In plain English
A medium-severity security flaw in AngleSharp from AngleSharp. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 26% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| NuGet | anglesharp | 1.5.0 | GHSA-pgww-w46g-26qg |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| AngleSharp | AngleSharp | < 1.5.0 |
Weakness: CWE-80 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:N