Vulnerability in AngleSharp (CVE-2026-54570)
Summary
Vulnerability in AngleSharp (CVE-2026-54570). Data can be tampered with by attackers. Exploitable via MathAnnotationXmlElement. Mitigation: upgrade to 1.5.0 or later.
Original description
The description as published by the source.
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.
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-54570 has been found in AngleSharp.
Attackers can target a specific entry point like MathAnnotationXmlElement over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 6.9/10.
What to do: upgrade AngleSharp to 1.5.0 or later.
If unsure, ask your IT team or search "AngleSharp CVE-2026-54570" on the vendor's site.
CVE-2026-54570 (AngleSharp) — CWE-80 / CVSS v3 6.9
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: MathAnnotationXmlElement / HtmlTip / AllForeignExceptions / innerHTML
Patched: 1.5.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-80) exists in AngleSharp. Attackers reach the vulnerable code path via MathAnnotationXmlElement without authentication.
Check the vendor advisory for the affected versions of AngleSharp. Attack surface: MathAnnotationXmlElement / HtmlTip / AllForeignExceptions / innerHTML.
Severity: Medium (CVSS 6.9/10). Data can be tampered with by attackers.
Update to 1.5.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'AngleSharp' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'AngleSharp' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
AngleSharpを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade AngleSharp to 1.5.0ステージング環境で 1.5.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- patch github.com
- web github.com
- web github.com