CVE-2025-11419 is a vulnerability identified in Keycloak, an open-source identity and access management solution widely used for single sign-on and authentication services. The flaw arises from the lack of limits or throttling on TLS 1.2 client-initiated renegotiation requests. TLS renegotiation is a feature that allows clients and servers to renegotiate cryptographic parameters during an existing TLS session. However, if an attacker repeatedly triggers renegotiation requests without restriction, it can lead to excessive CPU consumption on the server side. This resource exhaustion results in a denial of service (DoS), making the Keycloak service unavailable to legitimate users. The vulnerability affects multiple versions, including 0, 26.2.0, and 26.4.0. Exploitation requires no authentication or user interaction, increasing the attack surface. The CVSS 3.1 score of 7.5 reflects a high severity, primarily due to the impact on availability and the ease of remote exploitation over the network. No known exploits have been reported in the wild yet, but the vulnerability represents a significant risk for organizations using Keycloak in production environments. The root cause is the absence of resource allocation controls or throttling mechanisms for TLS renegotiation requests, which should be addressed by patching or configuration changes.

The primary impact of CVE-2025-11419 is a denial of service condition caused by CPU resource exhaustion on Keycloak servers. This can disrupt authentication and authorization services, potentially halting access to critical applications and systems that depend on Keycloak for identity management. Organizations relying on Keycloak for single sign-on or federated identity may experience service outages, leading to operational downtime, productivity loss, and potential security risks if fallback authentication mechanisms are weak or unavailable. The vulnerability does not directly compromise confidentiality or integrity but severely affects availability. Given that no authentication is required to exploit this vulnerability, attackers can launch DoS attacks remotely and anonymously, increasing the risk of widespread disruption. This can be particularly damaging for enterprises, cloud service providers, and government agencies that use Keycloak to secure sensitive environments. The lack of known exploits in the wild currently reduces immediate risk, but the vulnerability remains a critical concern for proactive defense.

To mitigate CVE-2025-11419, organizations should implement the following specific measures: 1) Apply official patches or updates from Keycloak as soon as they become available that address TLS renegotiation throttling or resource allocation limits. 2) Configure the underlying TLS stack or server environment to limit or disable client-initiated TLS renegotiation requests if feasible, as this can prevent abuse of this feature. 3) Deploy network-level protections such as rate limiting or anomaly detection on TLS handshake traffic to identify and block excessive renegotiation attempts. 4) Monitor server CPU usage and TLS session renegotiation patterns to detect potential abuse early. 5) Consider deploying Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) with signatures or heuristics to detect and mitigate renegotiation-based DoS attacks. 6) Review and harden Keycloak deployment configurations to reduce attack surface, including restricting access to administrative endpoints and enforcing strong network segmentation. 7) Maintain incident response plans that include procedures for mitigating DoS attacks targeting authentication infrastructure. These steps go beyond generic advice by focusing on TLS renegotiation controls and proactive monitoring specific to this vulnerability.