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: ["*"]`.
INFO
Published Date :
2026-04-06T08:38:36.657Z
Last Modified :
2026-04-06T11:57:17.383Z
Source :
redhat
AFFECTED PRODUCTS
The following products are affected by CVE-2026-37977 vulnerability.
| Vendors | Products |
|---|---|
| Redhat |
|
REFERENCES
Here, you will find a curated list of external links that provide in-depth information to CVE-2026-37977.
