EUVD-2026-30887
GHSA-4x37-hw65-52w8
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Primary rating from NVD.
CVSS VectorNVD
Lifecycle Timeline
1Blast Radius
ecosystem impact- 61 maven packages depend on org.keycloak:keycloak-services (28 direct, 33 indirect)
Ecosystem-wide dependent count for version 26.6.2.
DescriptionCVE.org
A flaw was found in Keycloak. This access control vulnerability in Keycloak's OpenID Connect (OIDC) token introspection endpoint allows a confidential client to bypass audience restrictions. An attacker-controlled client with valid credentials can retrieve sensitive token claims intended for other resource servers, compromising the confidentiality of lightweight access tokens. This issue can be exploited remotely by any confidential client in the realm with valid credentials.
AnalysisAI
Audience restriction bypass in Keycloak's OpenID Connect token introspection endpoint exposes sensitive token claims to unauthorized confidential clients. Any attacker-controlled confidential client holding valid realm credentials can query the introspection endpoint and retrieve claims from lightweight access tokens issued to other resource servers - violating the isolation guarantees of audience-scoped tokens. No public exploit has been identified at time of analysis and the vulnerability is not listed in CISA KEV, but the low attack complexity and network-accessible vector make this a realistic threat in multi-tenant or multi-service Keycloak deployments where client isolation is a security boundary.
Technical ContextAI
Keycloak implements OpenID Connect and OAuth 2.0, including RFC 7662 token introspection, which allows a resource server to query an authorization server about the validity and metadata of an access token. Correctly implemented, the introspection endpoint must enforce audience (aud) restrictions - a client should only be able to introspect tokens it is the intended audience for. The flaw is an access control failure at this enforcement layer: the endpoint does not adequately validate whether the calling confidential client is a legitimate intended audience for the token being inspected. This allows cross-service token claim disclosure within the same Keycloak realm. The affected CPE is cpe:2.3:a:red_hat:red_hat_build_of_keycloak:*:*:*:*:*:*:*:*, covering Red Hat's supported distribution of Keycloak. No CWE has been formally assigned in the available data, but the root cause maps conceptually to CWE-863 (Incorrect Authorization) - a failure to enforce access control on a sensitive API operation.
RemediationAI
The primary remediation is to apply the vendor-supplied patch from Red Hat once released; however, no specific fixed version number has been confirmed in the available data - the Red Hat advisory at https://access.redhat.com/security/cve/CVE-2026-37979 and Bugzilla entry at https://bugzilla.redhat.com/show_bug.cgi?id=2455328 should be monitored for patch availability and exact fix version. As a compensating control while awaiting a patch, administrators should audit all confidential clients registered in affected realms and revoke credentials for any client whose legitimacy cannot be confirmed, since the attack requires a registered client with valid credentials. Additionally, restricting which clients are permitted to call the token introspection endpoint via Keycloak's policy configuration or a network-layer API gateway can reduce the attack surface - note that this may break legitimate introspection flows for resource servers that depend on it. Enabling detailed audit logging on the introspection endpoint can aid in detecting anomalous cross-audience introspection attempts during the remediation window.
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Same weakness CWE-284 – Improper Access Control
View allSame technique Authentication Bypass
View allVendor StatusVendor
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