GHSA-7fqc-p256-7pwj is a medium-severity (CVSS 5.9) CWE-668 vulnerability in Steeltoe.Security.Authentication.JwtBearer. O3 Security confirms whether GHSA-7fqc-p256-7pwj is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Steeltoe's static JWKS cache shared across schemes and never invalidated
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- 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-7fqc-p256-7pwj.
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-7fqc-p256-7pwj 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 369,023 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
Steeltoe.Security.Authentication.JwtBearer.NETSteeltoe.Security.Authentication.OpenIdConnect.NETSteeltoe.Security.Authentication.CloudFoundryBaseReal-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
Summary
The JWT signing key cache in TokenKeyResolver uses kid as the sole cache key without namespacing by authority. In applications with multiple JwtBearer schemes pointing to different identity providers, a key fetched for one scheme can satisfy token validation for another. Additionally, cached keys have no expiration, so rotated or revoked keys remain trusted until the application process restarts.
Impact
In multi-scheme deployments, an attacker who controls one identity provider's signing key can forge tokens accepted by other schemes within the same application. For all applications using TokenKeyResolver, a signing key removed from the identity provider's JWKS endpoint remains trusted indefinitely.
Mitigations
If an immediate upgrade is not possible:
- In multi-scheme deployments, configure only one
JwtBearerscheme per application when different identity providers are required. - Restart the application process after an identity provider signing key rotation to clear stale cached keys.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Steeltoe.Security.Authentication.JwtBearer | all versions | 4.2.0 |
| .NETNuGet | Steeltoe.Security.Authentication.OpenIdConnect | all versions | 4.2.0 |
| .NETNuGet | Steeltoe.Security.Authentication.CloudFoundryBase | all versions | 3.4.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Steeltoe.Security.Authentication.JwtBearer. 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 Steeltoe.Security.Authentication.JwtBearer to 4.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-7fqc-p256-7pwj 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-7fqc-p256-7pwj 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-7fqc-p256-7pwj. 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-7fqc-p256-7pwj in your dependencies?
O3 detects GHSA-7fqc-p256-7pwj across NuGet dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.