Description (CNA)
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 (CNA)
| Vendor / product | Versions |
|---|---|
| Red Hat / Red Hat build of Keycloak 26.4 | unaffected 26.4.13-1 before * |
| Red Hat / Red Hat build of Keycloak 26.4 | unaffected 26.4-19 before * |
| Red Hat / Red Hat build of Keycloak 26.4 | unaffected 26.4-19 before * |
| Red Hat / Red Hat build of Keycloak 26.4.13 | unaffected |
| Red Hat / Red Hat build of Keycloak 26.6 | unaffected 26.6.3-3 before * |
| Red Hat / Red Hat build of Keycloak 26.6 | unaffected 26.6-6 before * |
| Red Hat / Red Hat build of Keycloak 26.6 | unaffected 26.6-6 before * |
| Red Hat / Red Hat build of Keycloak 26.6.3 | unaffected |
CWE
CWE-346
References
- https://access.redhat.com/errata/RHSA-2026:25097
- https://access.redhat.com/errata/RHSA-2026:25098
- https://access.redhat.com/errata/RHSA-2026:30049
- https://access.redhat.com/errata/RHSA-2026:30050
- https://access.redhat.com/security/cve/CVE-2026-37977
- https://bugzilla.redhat.com/show_bug.cgi?id=2455324
ADP enrichment
No English description supplied.
No references supplied.