Keycloak Refresh Token Rotation Bypass via Atomicity Flaw
CVE-2026-1035 Published on January 21, 2026
Org.keycloak.protocol.oidc: keycloak refresh token reuse bypass via toctou race condition
A flaw was found in the Keycloak server during refresh token processing, specifically in the TokenManager class responsible for enforcing refresh token reuse policies. When strict refresh token rotation is enabled, the validation and update of refresh token usage are not performed atomically. This allows concurrent refresh requests to bypass single-use enforcement and issue multiple access tokens from the same refresh token. As a result, Keycloaks refresh token rotation hardening can be undermined.
Vulnerability Analysis
CVE-2026-1035 can be exploited with network access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality, with no impact on integrity, and no impact on availability.
Timeline
Reported to Red Hat.
Made public. 5 days later.
Weakness Type
What is a TOCTTOU Vulnerability?
The software checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the software to perform invalid actions when the resource is in an unexpected state. This weakness can be security-relevant when an attacker can influence the state of the resource between check and use. This can happen with shared resources such as files, memory, or even variables in multithreaded programs.
CVE-2026-1035 has been classified to as a TOCTTOU vulnerability or weakness.
Products Associated with CVE-2026-1035
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Affected Versions
Red Hat Build of Keycloak: Red Hat JBoss Enterprise Application Platform 8: Red Hat JBoss Enterprise Application Platform Expansion Pack: Red Hat Single Sign-On 7:Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.