Security Tracking Issue

Do not make this issue public.

Flaw:

Keycloak TLS Client-Initiated Renegotiation Denial of Service

Keycloak is vulnerable to a Denial of Service (DoS) attack due to the default JDK setting that permits Client-Initiated Renegotiation in TLS 1.2. An unauthenticated remote attacker can repeatedly initiate TLS renegotiation requests to exhaust server CPU resources, making the service unavailable. Immediate mitigation is available by setting the -Djdk.tls.rejectClientInitiatedRenegotiation=true Java system property in the Keycloak startup configuration.

Requirements to exploit

An attacker requires network access to any TLS-enabled endpoint on a Keycloak server. No authentication is required to launch the attack.

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