{"id":"CVE-2026-54570","aliases":["GHSA-pgww-w46g-26qg"],"url":"https://o3.security/vulnerability/CVE-2026-54570","summary":"AngleSharp: HTML5 Spec Compliance: mXSS via annotation-xml HTML Integration Point Bypass","details":"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.","published":"2026-08-18T17:39:51.827Z","modified":"2026-08-20T03:54:29.656312838Z","cvss":{"score":6.9,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:N"},"epss":{"score":0.00246,"percentile":0.15845,"asOf":"2026-09-07"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"NuGet","name":"AngleSharp","fixedVersion":"1.5.0"}],"fix":{"url":"https://github.com/AngleSharp/AngleSharp/commit/8033a5c690af9c2c443f58e34875343fa4cc1d07","label":"AngleSharp/AngleSharp@8033a5c"},"references":[{"type":"WEB","url":"https://github.com/AngleSharp/AngleSharp/releases/tag/1.5.0"},{"type":"ADVISORY","url":"https://github.com/AngleSharp/AngleSharp/security/advisories/GHSA-pgww-w46g-26qg"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54570.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54570"},{"type":"FIX","url":"https://github.com/AngleSharp/AngleSharp/commit/8033a5c690af9c2c443f58e34875343fa4cc1d07"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-20T03:54:29.656312838Z"}}