Junglewise Threat Intelligence

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

Vendors: NuGet, SteeltoeOSS.

Executive brief

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incorrectly reuse a security key from one provider to validate a user from another, or continue trusting a key that has been revoked.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.

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

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