Sustainsys.Saml2 Insufficient Identity Provider Issuer ValidationGHSA-fv2h-753j-9g39
HIGHGHSA-fv2h-753j-9g39 is a high-severity (CVSS 7.5) CWE-289 vulnerability in Sustainsys.Saml2. A fix is available for Sustainsys.Saml2 — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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-fv2h-753j-9g39.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
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 | 1.0.3dotnet add package Sustainsys.Saml2 --version 1.0.3 |
| .NETNuGet | Sustainsys.Saml2 | ≥ 2.0.0&&< 2.9.2 | 2.9.2dotnet add package Sustainsys.Saml2 --version 2.9.2 |
| .NETNuGet | Kentor.AuthServices | all versions | No fix |
Affected Products
saml2sustainsysDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Sustainsys.Saml2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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.
Frequently Asked Questions
Is GHSA-fv2h-753j-9g39 in your dependencies?
Find it across NuGet, including transitive dependencies.