Authorization bypass through user-controlled key in Keycloak - CVE-2026-9087
Published: September 5, 2026
Vulnerability identifier: #VU146990
CSH Severity: Low
CVSS v4: 7.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-9087
CWE-ID: CWE-639
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to compromise a victim\'s local account.
The vulnerability exists due to insufficient verification proof scoping in the cross-session verification proof mechanism when linking identity provider accounts. A remote user can use a verification proof for a victim\'s local account to link a second upstream account on the same identity provider and compromise a victim\'s local account.
User interaction is required.
Affected software
Keycloak
Red Hat build of Keycloak
Red Hat build of Keycloak
How to mitigate CVE-2026-9087
Install security update from vendor's website.
Keycloak - update to 26.6.3
Red Hat build of Keycloak - addressed in versions 26.4.13, 26.6.3
Red Hat build of Keycloak - addressed in versions 26.4.13, 26.6.3