This advisory covers Red Hat OpenShift Container Platform 4.17.56, which contains fixes for several bugs and security vulnerabilities, including CVE-2026-12151. The CVE-2026-12151 vulnerability is a denial of service issue in the undici WebSocket client library, where a malicious WebSocket server can send many small or empty continuation frames that bypass validation checks, causing unbounded memory growth in the client process. This leads to memory exhaustion and denial of service for applications using the affected undici WebSocket client or WebSocketStream API. The advisory provides updated container images and RPM packages to address these issues. Users should upgrade their clusters following the official Red Hat OpenShift upgrade documentation.

The primary impact is a critical denial of service vulnerability that can be exploited remotely without authentication. An attacker controlling a malicious WebSocket server can cause unbounded memory growth in the client by sending crafted WebSocket frames, leading to memory exhaustion and service disruption in affected Red Hat OpenShift Container Platform deployments using the undici WebSocket client. This affects availability but does not impact confidentiality or integrity.

A fix is available in Red Hat OpenShift Container Platform version 4.17.56. Users should upgrade to this version using the official upgrade procedures documented by Red Hat. No effective mitigations other than applying the update are currently available or meet Red Hat's criteria for deployment and stability. Administrators should monitor Red Hat's official channels for updated release notes and upgrade instructions.