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TI-2026-39405 Aliases CVE-2026-54570GHSA-pgww-w46g-26qg

AngleSharp: HTML5 Spec Compliance: mXSS via annotation-xml HTML Integration Point Bypass

Priority MEDIUM 64CWE-80Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
High
Impact type
Cross-site scripting
Confidentiality · integrity · availability
Low · High · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-80.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00331 26th percentileScored 2026-11-07
Fix Fixed AngleSharp (AngleSharp): 1.5.0AngleSharp (NuGet): 1.5.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
AngleSharpAngleSharpbefore 1.5.01.5.0Patch availableCNA
—AngleSharp (NuGet)before 1.5.01.5.0Patch availableGHSA-pgww-w46g-26qg
  • AngleSharp VendorAngleSharp Affected before 1.5.0 Fixed in 1.5.0 Patch available CNA
  • AngleSharp (NuGet) Vendor— Affected before 1.5.0 Fixed in 1.5.0 Patch available GHSA-pgww-w46g-26qg

Remediation

  • Fix · CNA AngleSharp (AngleSharp) Fixed in 1.5.0
  • Fix · GHSA-pgww-w46g-26qg AngleSharp (NuGet) Fixed in 1.5.0 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-54570
  2. 2026-10-03 Alias added: GHSA-pgww-w46g-26qg

References

Other 4

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences