CVE-2026-117859: Keycloak-services: keycloak-services: par single-use bypass via flow restart
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 AUTHORIZATIONREQUESTURI 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 redirecturi, scope, state, and nonce. Consequently, when authentication completes after a flow restart, the PAR consumption check is skipped, leaving the requesturi active in the single-use store. An attacker can replay the same requesturi 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.
Other sources
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.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What conditions are required to exploit this issue?
An attacker needs low privileges and must be able to trigger an authentication flow restart after using a pushed authorization request. They can then replay the same request_uri while it remains valid.
How long is the replay window?
The request_uri remains replayable for its valid lifespan, which is 60 seconds by default. Within that window, the attacker can obtain a second authorization grant and distinct access token from the same pushed request.
How can I identify possible exploitation?
Review authorization activity for the same PAR request_uri being used more than once, particularly where an authentication flow restart occurred before authentication completed. Repeated authorization codes or access tokens associated with one pushed request indicate that the single-use guarantee may have been bypassed.