Bug 2455328 (CVE-2026-37979)

Summary: CVE-2026-37979 keycloak: Keycloak: Information disclosure via OIDC token introspection endpoint audience bypass
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: aschwart, aszczucz, boliveir, drichtar, mposolda, pjindal, rmartinc, security-response-team, ssilvert, sthorger, vmuzikar
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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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.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Deadline: 2026-06-23   

Description OSIDB Bzimport 2026-04-06 07:58:16 UTC 
Access control vulnerability in Keycloak’s OIDC token introspection endpoint. The flaw is caused by not enforcing that the introspecting client is included in the token’s aud claim before returning introspection results. When a confidential attacker-controlled client obtains or intercepts an access token issued to a different audience, it can call the introspection endpoint and receive the full claim set, including claims intentionally omitted from lightweight access tokens. This can be exploited remotely by any confidential client in the realm with valid credentials. The vulnerability breaks the confidentiality model of lightweight tokens and allows unintended clients to recover sensitive attributes meant only for the legitimate resource server.