Bug 2501735 (CVE-2026-16102)

Summary: CVE-2026-16102 keycloak-services: keycloak-services: Default DCR policy allows role forgery via User Property mappers
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerability-draftAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: anujha, aschwart, asoldano, aszczucz, bbaranow, bmaxwell, boliveir, bstansbe, dlofthou, drichtar, istudens, ivassile, iweiss, mosmerov, mposolda, msvehla, nwallace, pberan, pesilva, pjindal, pmackay, rmartinc, rstancel, security-response-team, ssilvert, sthorger, thjenkin, vdosoudi, 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 (DCR) component of Keycloak, an identity and access management solution. The default DCR policy fails to properly validate the claim path for User Property mappers, allowing them to write values to sensitive internal claim locations. An attacker with a standard user account and a limited Initial Access Token can exploit this to forge administrative roles in their access token. This allows the attacker to take over other clients, steal confidential secrets, and potentially gain full administrative control over the realm.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Deadline: 2026-10-13   

Description OSIDB Bzimport 2026-07-17 14:39:29 UTC 
A flaw was found in Keycloak where the default Dynamic Client Registration (DCR) policy permits the use of User Property mappers without validating the target claim path. While the policy checks the mapper provider type, it does not restrict where the mapper can write data within the resulting token.
An attacker with a standard user account and a limited Initial Access Token (IAT) can register a new client and configure User Property mappers (such as firstName or lastName) to target the resource_access.realm-management.roles claim path. By setting their user profile properties to administrative role names (e.g., manage-clients, realm-admin), the attacker can produce a forged access token containing these roles.
Although recent mitigations (CVE-2026-4629) protect the Admin REST API from such forged tokens, the Client Registration API remains vulnerable because it reads the resource_access claim directly during authorization. An attacker can use this bypass to perform unauthorized DCR operations, including reading confidential client secrets, modifying redirect URIs, and impersonating service accounts to achieve full realm compromise.