CVE-2024-3653 is a vulnerability identified in Undertow, a Java-based web server widely used in various enterprise applications. The issue stems from the learning-push handler component, which is disabled by default. When enabled without configuring the maxAge parameter, which defaults to -1, the handler fails to release memory after its effective lifetime. This leads to a memory leak condition where allocated memory is retained indefinitely, potentially causing resource exhaustion on the server. An attacker can exploit this vulnerability by sending standard HTTP requests to the server, without requiring any authentication or user interaction. The vulnerability affects availability by potentially causing denial of service due to memory depletion. The CVSS 3.1 score of 5.3 reflects a medium severity, with network attack vector, low attack complexity, no privileges required, and no user interaction needed. No confidentiality or integrity impact is observed. Currently, there are no known exploits in the wild, and no official patches have been linked, although configuration changes can mitigate the risk. The vulnerability highlights the importance of secure default configurations and proper resource management in server components.

For European organizations, this vulnerability could lead to denial of service conditions on servers running Undertow with the learning-push handler enabled and default maxAge settings. This can disrupt web services, affecting business continuity and user access. Organizations relying on Undertow for critical applications may experience degraded performance or outages if exploited. While the vulnerability does not compromise data confidentiality or integrity, the availability impact can have significant operational consequences, especially for public-facing services or internal applications with high availability requirements. The medium severity rating suggests that while the risk is not critical, it should not be ignored, particularly in environments with high traffic volumes or limited server resources. The absence of known exploits reduces immediate risk but does not eliminate the need for proactive mitigation.

1. Disable the learning-push handler in Undertow server configurations if it is not required for your application functionality. 2. If the learning-push handler must be enabled, explicitly set the maxAge configuration parameter to a non-negative value to ensure timely release of memory resources. 3. Monitor server memory usage closely to detect abnormal increases that may indicate exploitation attempts. 4. Apply any forthcoming patches or updates from Undertow or Red Hat promptly once available. 5. Conduct regular configuration audits to ensure default or insecure settings are not inadvertently enabled in production environments. 6. Implement resource limits and alerts at the operating system or container level to mitigate impact from potential memory leaks. 7. Consider deploying web application firewalls or network-level protections to limit exposure to untrusted HTTP requests targeting this vulnerability.