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CWE-80Weakness · CWE-80

CVE-2026-54570

MEDIUM · 6.9 CVSS v3.1 Published 2026-08-18
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
76/100
Remediation priority · High
Remotely reachable No privileges Patch available Brand new

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:N

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch github.com →
Recommended fix High confidence

AngleSharp 1.5.0

  1. Identify the AngleSharp package reference in your project (check .csproj file, packages.config, or .nuspec)
  2. Update the AngleSharp package to version 1.5.0 or later using your preferred method: NuGet Package Manager (`Install-Package AngleSharp -Version 1.5.0`), dotnet CLI (`dotnet add package AngleSharp --version 1.5.0`), or manually edit the version in your project file
  3. Rebuild the project to ensure the new version is correctly integrated
  4. Re-test any functionality that uses AngleSharp parsing to verify the upgrade does not break existing behavior
  5. Ensure your application's dependency lock/pinning files (like packages.lock.json) are updated to reflect the new version
Caveat Review release notes for 1.5.0 to check for any breaking changes in parsing behavior; the library may have altered DOM construction logic

Generated from the published advisory — verify against the referenced sources before acting.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-54570 in production — separate from our analysis above.

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