Description
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.
References3
Metrics
- CVSS 3.1
-
6.8
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N - EPSS — exploit probability
- 0% percentile: 5 · as of 9 November 2026
- CWE
- CWE-287
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.