CVE-2024-3653 is a vulnerability identified in the Undertow web server, specifically related to the learning-push handler component. The issue arises when the learning-push handler is enabled in the server configuration, which is not the default setting. If enabled without explicitly configuring the maxAge parameter, it defaults to -1, causing the handler to fail to release memory after the effective lifetime of cached data. This leads to a memory leak condition, where memory consumption grows over time as the server processes normal HTTP requests. An attacker can exploit this vulnerability remotely by sending crafted HTTP requests to the server, triggering the memory leak without requiring authentication or user interaction. The vulnerability does not compromise data confidentiality or integrity but impacts system availability by potentially exhausting server memory resources, leading to denial of service (DoS). The vulnerability has a CVSS 3.1 base score of 5.3, categorized as medium severity, reflecting the moderate impact and ease of exploitation. The vulnerability is mitigated if the maxAge configuration is set to a valid value or if the learning-push handler remains disabled. No known exploits are currently reported in the wild. This vulnerability is particularly relevant for environments running Undertow with the learning-push handler enabled and default maxAge settings, which may be present in some Java-based web applications and middleware stacks.

For European organizations, the primary impact of CVE-2024-3653 is the potential for denial of service due to memory exhaustion on servers running Undertow with the vulnerable configuration. This can disrupt web services, leading to downtime and degraded performance, affecting business continuity and user experience. Critical infrastructure and public sector services relying on Java-based web servers could face operational interruptions. While the vulnerability does not expose sensitive data or allow unauthorized access, the availability impact can indirectly affect confidentiality and integrity by causing system instability. Organizations with high traffic web applications or limited server resources are at greater risk of experiencing service outages. The lack of authentication or user interaction requirements means attackers can exploit this remotely and anonymously, increasing the threat surface. European companies in finance, healthcare, government, and telecommunications sectors, which often rely on robust web services, may face reputational damage and compliance risks if services are disrupted.

To mitigate CVE-2024-3653, organizations should first verify if the learning-push handler is enabled in their Undertow server configurations. If it is not required, the safest approach is to disable the handler entirely to eliminate the attack vector. If the handler must be enabled, explicitly configure the maxAge parameter with a valid positive value to ensure proper memory release after the effective lifetime. Regularly monitor server memory usage to detect abnormal growth patterns indicative of exploitation attempts. Apply any available patches or updates from Undertow maintainers as soon as they are released. Additionally, implement network-level protections such as rate limiting and web application firewalls (WAFs) to reduce the risk of exploitation by limiting the volume of malicious HTTP requests. Conduct security audits and penetration testing focused on memory management vulnerabilities in web server components. Maintain an inventory of applications using Undertow to prioritize remediation efforts based on exposure and criticality.