CVE-2025-11419: Keycloak: keycloak tls client-initiated renegotiation denial of service

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-12-23 · updated 2026-10-19
Weakness: CWE-770

Description

A flaw was found in Keycloak. This vulnerability allows an unauthenticated remote attacker to cause a denial of service (DoS) by repeatedly initiating TLS 1.2 client-initiated renegotiation requests to exhaust server CPU resources, making the service unavailable.

Affected products

Red Hat build of Keycloak 26.4: all versions — fixed in 26.0-20, 26.0-21, 26.0.16-2, 26.2-11, 26.2.10-2

How to fix

Upgrade to a fixed version: Red Hat build of Keycloak 26.4 26.0-20, 26.0-21, 26.0.16-2, 26.2-11. Check the vendor advisory for mitigations.

References

https://access.redhat.com/errata/RHSA-2025:18254
https://access.redhat.com/errata/RHSA-2025:18255
https://access.redhat.com/errata/RHSA-2025:18889
https://access.redhat.com/errata/RHSA-2025:18890
https://access.redhat.com/security/cve/CVE-2025-11419
https://bugzilla.redhat.com/show_bug.cgi?id=2402142
https://github.com/keycloak/keycloak/discussions/25209
https://github.com/keycloak/keycloak/issues/43020

Get alerted when CVE-2025-11419 or the next vulnerability affects your stack