vulnerability / NVI-00016189 / Revision 1
AngleSharp HTML5 Spec Compliance: mXSS via annotation-xml HTML Integration Point Bypass
GitHub lists this reviewed advisory for AngleSharp. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
6.9 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
AngleSharp
source listed< 1.5.0
### Summary The HTML specification requires that a MathML `` element with `encoding="text/html"` or `encoding="application/xhtml+xml"` is treated as an HTML integration point. Content inside it must be parsed as HTML, not MathML. AngleSharp does not implement this correctly. As a result, the parser produces a DOM tree that differs from what a browser will build (different namespaces if `encoding="text/html"` is not treated) when given the same serialized output. Two bugs combine to make this exploitable: - Missing HtmlTip flag: MathAnnotationXmlElement is never assigned NodeFlags.HtmlTip based on its encoding attribute, so the Consume() dispatch always routes tokens to Foreign() instead of Home() (HTML mode). - Unescaped in attribute values: HtmlMarkupFormatter.WriteAttributeValue() does not escape characters, only & and ". This allows injected markup to break out of attribute values on re-parse. _See Escape "" in attributes when serializing HTML #6235 _ ### Details In `MathAnnotationXmlElement` (`AngleSharp/Mathml/Dom/Internal/MathAnnotationXmlElement.cs`): ```cs // Current — HtmlTip is never set
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-pgww-w46g-26qg ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.