GHSA-43cp-6p3q-2pc4 is a medium-severity (CVSS 6.1) vulnerability in HtmlSanitizer. A fix is available for HtmlSanitizer — see the affected versions and patch details below.
HtmlSanitizer vulnerable to Cross-site Scripting in Foreign Content
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-43cp-6p3q-2pc4.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-43cp-6p3q-2pc4 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 379,145 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
HtmlSanitizer.NETHtmlSanitizerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
Description
Impact
The vulnerability occurs in configurations where foreign content is allowed, i.e. either svg or math are in the list of allowed elements.
Specifically, the requirements for the vulnerability are:
- Allowing one foreign element:
svg, ormath - Comments or one raw text element:
iframe,noembed,xmp,title,noframes,styleornoscript
Configurations that meet the above requirements plus the following are vulnerable to an additional vulnerability:
- Any HTML integration element:
title,desc,mi,mo,mn,ms,mtext,annotation-xml.
In case an application sanitizes user input with a vulnerable configuration, an attacker could bypass the sanitization and inject arbitrary HTML, including JavaScript code.
Note that in the default configuration the vulnerability is not present.
Patches
The vulnerability has been fixed in versions 8.0.723 and 8.1.722-beta (preview version).
Workarounds
Disallow foreign elements svg and math. This is the case in the default configuration, which is therefore not affected by the vulnerability.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | HtmlSanitizer | all versions | 8.0.723dotnet add package HtmlSanitizer --version 8.0.723 |
| .NETNuGet | HtmlSanitizer | ≥ 8.1.0-beta&&< 8.1.722-beta | 8.1.722-betadotnet add package HtmlSanitizer --version 8.1.722-beta |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for HtmlSanitizer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update HtmlSanitizer to 8.0.723 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-43cp-6p3q-2pc4 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-43cp-6p3q-2pc4 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-43cp-6p3q-2pc4. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-43cp-6p3q-2pc4 in your dependencies?
O3 Security finds GHSA-43cp-6p3q-2pc4 across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.