Steeltoe is an open source project that provides a collection of libraries that helps users build cloud-native applications. In Steeltoe.Security.Authentication.CloudFoundryBase prior to version 3.4.0, Steeltoe.Security.Authentication.JwtBearer prior to version 4.2.0, and Steeltoe.Security.Authentication.OpenIdConnect prior to version 4.2.0, 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. Steeltoe.Security.Authentication.CloudFoundryBase version 3.4.0, Steeltoe.Security.Authentication.JwtBearer version 4.2.0, and Steeltoe.Security.Authentication.OpenIdConnect version 4.2.0 patch the issue. If an immediate upgrade is not possible: In multi-scheme deployments, configure only one "JwtBearer" scheme per application when different identity providers are required; and/or restart the application process after an identity provider signing key rotation to clear stale cached keys.