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CVE-2026-37977— Keycloak: org.keycloak.protocol.oidc.grants.ciba: keycloak: information disclosure via cors header injection due to unvalidated jwt azp claim

CVSS 3.7 · Low EPSS 0.01% · P1
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I. Basic Information for CVE-2026-37977

Vulnerability Information
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Vulnerability Title
Keycloak: org.keycloak.protocol.oidc.grants.ciba: keycloak: information disclosure via cors header injection due to unvalidated jwt azp claim
Source: NVD (National Vulnerability Database)
Vulnerability 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: ["*"]`.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
源验证错误
Source: NVD (National Vulnerability Database)
Vulnerability Title
Keycloak 访问控制错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Keycloak是Keycloak开源的一种开源身份和访问管理解决方案。 Keycloak存在访问控制错误漏洞，该漏洞源于用户管理访问令牌端点存在跨域资源共享标头注入，可能导致授权服务器错误响应中的低敏感性信息泄露。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

VendorProductAffected VersionsCPESubscribe
Red HatRed Hat Build of Keycloak-cpe:/a:redhat:build_keycloak:

II. Public POCs for CVE-2026-37977

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III. Intelligence Information for CVE-2026-37977

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Same Patch Batch · Red Hat · 2026-04-06 · 3 CVEs total

CVE-2026-56735.6 MEDIUMLibtheora: libtheora: denial of service or information disclosure via malformed avi file p
CVE-2026-57045.0 MEDIUMTar: tar: hidden file injection via crafted archives

IV. Related Vulnerabilities

Same product: Red Hat Build of Keycloak
Same vendor: Red Hat
Same weakness: CWE-346

V. Comments for CVE-2026-37977

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