Keycloak provides a feature called mTLS holder-of-key binding which ensures that a token can only be used by the client that originally requested it by binding it to their digital certificate.

Keycloak provides a feature called mTLS holder-of-key binding which ensures that a token can only be used by the client that originally requested it by binding it to their digital certificate. A flaw was discovered where the new Standard Token Exchange V2 feature does not check for this certificate. This allows an attacker with stolen client credentials to obtain a standard, unrestricted token that bypasses these security protections.

CVSS 3.1

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

Severity from

no source yet

Weakness

CWE-287

• www.cve.org/CVERecord?id=CVE-2026-97846
• nvd.nist.gov/vuln/detail/CVE-2026-97846
• access.redhat.com/security/cve/CVE-2026-97846
• bugzilla.redhat.com/show_bug.cgi?id=2540949