CVE-2025-59089 affects the latchset kdcproxy component, which acts as a proxy for Kerberos Key Distribution Center (KDC) communications. The vulnerability arises because kdcproxy does not impose limits or throttling on the size of TCP responses it receives from KDC servers. An attacker who can induce kdcproxy to connect to a malicious KDC server—potentially via server-side request forgery—can exploit this by sending oversized or malformed Kerberos responses. Specifically, kdcproxy copies the entire buffered TCP stream into a new buffer on each recv() call, even if the transfer is incomplete, causing excessive memory allocation and CPU usage. Furthermore, kdcproxy continues to accept incoming response chunks as long as the total received data length does not exactly match the length indicated in the response header, even if individual chunks or the total exceed the maximum allowed Kerberos message size. This allows an attacker to send unbounded data until the connection times out (approximately 12 seconds), exhausting server memory and CPU resources. When multiple such requests occur concurrently, the accept queue can overflow, resulting in denial of service to legitimate clients. The vulnerability does not impact confidentiality or integrity, and no authentication or user interaction is required to exploit it. The CVSS 3.1 base score is 5.9, reflecting a network attack vector with high attack complexity but no privileges or user interaction needed, and a high impact on availability only. No known exploits are currently reported in the wild. The affected product version is 0, indicating early or initial releases of kdcproxy. No patches or mitigations are linked yet, so organizations must implement defensive controls to mitigate risk.

For European organizations, this vulnerability poses a significant risk to the availability of Kerberos authentication services when using latchset kdcproxy. Kerberos is widely used in enterprise environments for secure authentication, and disruption of kdcproxy can lead to authentication failures, impacting access to critical systems and services. This can cause operational downtime, loss of productivity, and potential cascading effects on dependent applications. Since the attack can be launched remotely without authentication, exposed kdcproxy instances are at risk of denial-of-service attacks that could degrade or completely block legitimate user authentication. Organizations in sectors relying heavily on Kerberos for identity management—such as government, finance, telecommunications, and large enterprises—may face increased risk. The medium severity rating reflects that while confidentiality and integrity are not compromised, the availability impact can be disruptive. The lack of known exploits suggests a window for proactive mitigation before widespread attacks occur.

To mitigate CVE-2025-59089, European organizations should first identify and inventory all deployments of latchset kdcproxy, especially those exposed to untrusted networks. Network segmentation and firewall rules should restrict access to kdcproxy to trusted KDC servers and authorized clients only, minimizing exposure to attacker-controlled servers. Implementing strict egress filtering to prevent kdcproxy from connecting to arbitrary external KDC servers can reduce the risk of server-side request forgery exploitation. Monitoring network traffic for abnormal or oversized Kerberos responses can help detect exploitation attempts. Applying rate limiting or connection throttling at the network or application layer can mitigate resource exhaustion from concurrent attacks. Organizations should engage with latchset or their vendors to obtain patches or updates addressing this vulnerability once available. In the interim, consider deploying Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) with custom rules to detect and block anomalous Kerberos traffic patterns. Finally, ensure robust logging and alerting on kdcproxy resource usage and connection anomalies to enable rapid incident response.