Time-of-check Time-of-use (TOCTOU) Race Condition in Keycloak - CVE-2026-1035
Published: September 10, 2026
Vulnerability identifier: #VU148926
CSH Severity: Low
CVSS v4: 2.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-1035
CWE-ID: CWE-367
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to bypass single-use refresh token enforcement.
The vulnerability exists due to a time-of-check time-of-use race condition in the TokenManager class during refresh token processing when strict refresh token rotation is enabled. A remote user can send concurrent refresh requests using the same refresh token to bypass single-use refresh token enforcement.
Affected software
Keycloak
Red Hat build of Keycloak
Red Hat build of Keycloak
How to mitigate CVE-2026-1035
Install security update from vendor's website.
Keycloak - update to 26.5.6
Red Hat build of Keycloak - update to 26.4.11
Red Hat build of Keycloak - update to 26.4.11