Bug 2545802 (CVE-2026-105306)

Summary: CVE-2026-105306 keycloak-services: keycloak-services: Token introspection audience bypass via Dynamic Client Registration
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, ssilvert, sthorger, vmuzikar
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Dynamic Client Registration flow of the Keycloak identity and access management server. The issue occurs because the registration process fails to filter security-sensitive client attributes when a new client is created. An attacker with a valid Initial Access Token can register a client that bypasses audience checks during token introspection. This allows the attacker to view sensitive identity information, roles, and session details from access tokens belonging to other applications in the same realm.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-10-05 05:41:12 UTC 
A vulnerability was found in Keycloak where the Dynamic Client Registration (DCR) flow does not properly filter sensitive client attributes. Specifically, a registrant using an Initial Access Token can set the internal attribute allow.token.introspection.without.audience.check during the registration process. This attribute disables the mandatory audience verification on the token introspection endpoint.
To exploit this flaw, an attacker must possess a valid Initial Access Token for a realm where DCR is enabled. By registering a malicious client with this attribute, the attacker can then use that client's credentials to introspect any active access token they have obtained or intercepted from other clients in the same realm. Successful exploitation results in the disclosure of the full claim set of the token, including user identity, roles, scopes, and session IDs, regardless of whether the introspecting client was the intended audience. This is a bypass of the security controls introduced to fix CVE-2026-37979.