CVE-2026-50202: Steeltoe Security JWT signing key cache collision and lack of expiration

CVE-2026-50202 · Severity: medium · CVSS 5.9 · Published 2026-06-17

Steeltoe, a framework for building cloud-native applications, contains a flaw in how it handles security keys used to verify user identities. In systems using multiple identity providers, the software may incorrectly reuse a security key from one provider to validate a user from another, or continue trusting a key that has been revoked. This could allow an attacker who controls one identity provider to forge credentials that are accepted by other parts of the application, potentially leading to unauthorized access.

Vendors: NuGet, SteeltoeOSS.

Quick answers

Is CVE-2026-50202 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-50202 being exploited in the wild.
How severe is CVE-2026-50202?
Medium severity, with a CVSS score of 5.9, published 17 June 2026.
Which products and versions are affected?
Steeltoe.Security.Authentication.CloudFoundryBase (NuGet) ECOSYSTEM:introduced=0,fixed=3.4.0; Steeltoe.Security.Authentication.JwtBearer (NuGet) ECOSYSTEM:introduced=0,fixed=4.2.0; Steeltoe.Security.Authentication.OpenIdConnect (NuGet) ECOSYSTEM:introduced=0,fixed=4.2.0; SteeltoeOSS Security.Authentication.CloudFoundryBase <= 3.3.0; and 5 more.
Is there a fix for CVE-2026-50202?
Yes. Steeltoe.Security.Authentication.CloudFoundryBase (NuGet): upgrade to 3.4.0 or later; Steeltoe.Security.Authentication.JwtBearer (NuGet): upgrade to 4.2.0 or later; Steeltoe.Security.Authentication.OpenIdConnect (NuGet): upgrade to 4.2.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-50202 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-50202?
Check whether you run Steeltoe.Security.Authentication.CloudFoundryBase (NuGet), Steeltoe.Security.Authentication.JwtBearer (NuGet), Steeltoe.Security.Authentication.OpenIdConnect (NuGet) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • Steeltoe.Security.Authentication.CloudFoundryBase (NuGet): upgrade to 3.4.0 or later
    dotnet add package Steeltoe.Security.Authentication.CloudFoundryBase --version 3.4.0
  • Steeltoe.Security.Authentication.JwtBearer (NuGet): upgrade to 4.2.0 or later
    dotnet add package Steeltoe.Security.Authentication.JwtBearer --version 4.2.0
  • Steeltoe.Security.Authentication.OpenIdConnect (NuGet): upgrade to 4.2.0 or later
    dotnet add package Steeltoe.Security.Authentication.OpenIdConnect --version 4.2.0

Technical details

The vulnerability exists in the TokenKeyResolver component, where the JWT signing key cache uses the Key ID (kid) as the sole cache key without namespacing it by the authority/issuer. In multi-scheme deployments, a key fetched for one JwtBearer scheme can satisfy validation for another. Furthermore, the cache lacks an expiration mechanism, meaning rotated or revoked keys remain trusted until the application process is restarted. An attacker controlling one identity provider's signing key could forge tokens accepted by other schemes within the same application. Patches are available in versions 3.4.0 and 4.2.0.

Affected products

  • SteeltoeOSS Steeltoe.Security.Authentication.JwtBearer <= 4.1.0
  • SteeltoeOSS Steeltoe.Security.Authentication.OpenIdConnect <= 4.1.0
  • SteeltoeOSS Steeltoe.Security.Authentication.CloudFoundryBase <= 3.3.0

Identifiers

  • CVE-2026-50202
  • GHSA-7fqc-p256-7pwj

Timeline

  • 2026-05-29: disclosed: Advisory published by TimHess
  • 2026-06-17: advisory: NVD publication date
  • 2026-07-02: patched: GitHub Advisory Database entry updated/reviewed

References

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