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3.7 Low

CVE-2026-37977 A flaw was found in Keycloak

Description

A flaw was found in Keycloak. A remote attacker can exploit a Cross-Origin Resource Sharing (CORS) header injection vulnerability in Keycloak's User-Managed Access (UMA) token endpoint. This flaw occurs because the `azp` claim from a client-supplied JSON Web Token (JWT) is used to set the `Access-Control-Allow-Origin` header before the JWT signature is validated. When a specially crafted JWT with an attacker-controlled `azp` value is processed, this value is reflected as the CORS origin, even if the grant is later rejected. This can lead to the exposure of low-sensitivity information from authorization server error responses, weakening origin isolation, but only when a target client is misconfigured with `webOrigins: ["*"]`.

Affected products and versions

Product Affected versions Fixed in
Red Hat Build of Keycloak Versions not published
Red Hat build of Keycloak 26.6.3 Versions not published
Red Hat build of Keycloak 26.6 26.6 earliest → < 26.6-6 26.6-6
Red Hat build of Keycloak 26.6.4 Versions not published
Red Hat build of Keycloak 26.4 26.4 earliest → < 26.4-19 26.4-19
Red Hat build of Keycloak 26.4.13 Versions not published

References

Timeline

  1. Published
  2. Last modified

Other CVEs of Red Hat Build of Keycloak

The 276 CVEs of Red Hat Build of Keycloak →
CVE-2026-9797 Keycloak: keycloak: privilege escalation via client authentication manipulation by an authenticated administrator 6.5 Medium CVE-2026-97848 Keycloak-services: keycloak-services: protocol mapper with jsontype=json bypasses token sanitization 6.5 Medium CVE-2026-97367 Keycloak-services: keycloak-services: dcr azp and sid claim substitution allows account rest session takeover 6.4 Medium CVE-2026-96547 Keycloak-services: keycloak-services: dcr registration-time claim-path gap allows forging realm_access.roles 6.5 Medium
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