Bug 2561991 (CVE-2026-117859)

Summary: CVE-2026-117859 keycloak-services: keycloak-services: PAR single-use bypass via flow restart
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 Pushed Authorization Request PAR implementation of the keycloak-services component. The issue occurs when an authentication flow is restarted, which incorrectly clears the internal markers used to track PAR consumption while leaving the request active. This allows an attacker to reuse the same authorization request to obtain multiple access tokens, bypassing security requirements for single-use requests.
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Description OSIDB Bzimport 2026-10-27 14:03:36 UTC 
A flaw was found in Keycloaks Pushed Authorization Request PAR implementation. The fix for CVE-2026-96446 moved PAR consumption to authentication completion by checking for the AUTHORIZATION_REQUEST_URI authentication session note. However, triggering an authentication flow restart via /login-actions/restart clears authentication session notes while preserving client notes including request parameters such as redirect_uri, scope, state, and nonce. Consequently, when authentication completes after a flow restart, the PAR consumption check is skipped, leaving the request_uri active in the single-use store.
An attacker can replay the same request_uri within its valid lifespan default 60 seconds to obtain a second authorization grant and distinct access token. This bypasses the single-use guarantee required by RFC 9126. Successful exploitation allows an attacker to mint multiple authorization codes and access tokens from a single pushed request.