GHSA-fv2h-753j-9g39
HIGHSustainsys.Saml2 Insufficient Identity Provider Issuer Validation
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.
Blast Radius
Sustainsys.Saml2.NETSustainsys.Saml2.NETKentor.AuthServicesReal-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
When a response is processed, the issuer of the Identity Provider is not sufficiently validated. This could allow a malicious identity provider to craft a Saml2 response that is processed as if issued by another identity provider. It is also possible for a malicious end user to cause stored state intended for one identity provider to be used when processing the response from another provider.
An application is impacted if they rely on any of these features in their authentication/authorization logic:
- the issuer of the generated identity and claims
- items in the stored request state (AuthenticationProperties)
Patches
Patched in version 2.9.2 and 1.0.3. All previous versions are vulnerable.
Workarounds
The AcsCommandResultCreated notification can be used to add the validation required if an upgrade to patched packages is not possible.
References
The patch is linked to https://github.com/Sustainsys/Saml2/issues/712 and https://github.com/Sustainsys/Saml2/issues/713
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Sustainsys.Saml2 | all versions | 1.0.3 |
| .NETNuGet | Sustainsys.Saml2 | ≥ 2.0.0&&< 2.9.2 | 2.9.2 |
| .NETNuGet | Kentor.AuthServices | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Sustainsys.Saml2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update Sustainsys.Saml2 to 1.0.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fv2h-753j-9g39 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 pinpoints whether GHSA-fv2h-753j-9g39 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-fv2h-753j-9g39. 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-fv2h-753j-9g39 in your dependencies?
O3 detects GHSA-fv2h-753j-9g39 across NuGet dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.