# CVE-2026-54570

## Summary

- **CVE ID:** CVE-2026-54570
- **Severity:** MEDIUM
- **CVSS Score:** 6.9 (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:N)
- **CWE:** CWE-80
- **Published:** Aug 18, 2026
- **Last Modified:** Aug 18, 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.

## Affected Products

- AngleSharp — AngleSharp (< 1.5.0)

## References

- [CNA](https://github.com/AngleSharp/AngleSharp/security/advisories/GHSA-pgww-w46g-26qg)
- [CNA](https://github.com/AngleSharp/AngleSharp/commit/8033a5c690af9c2c443f58e34875343fa4cc1d07)
- [CNA](https://github.com/AngleSharp/AngleSharp/releases/tag/1.5.0)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.25%
- **EPSS Percentile:** 15.9

---
_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._