CVE-2024-3653 is a vulnerability identified in Undertow, a flexible Java web server. The issue arises when the learning-push handler is enabled in the server configuration, which is disabled by default. If enabled without explicitly setting the maxAge configuration parameter, it defaults to -1, causing the handler to fail to release memory after the effective lifetime of certain data. This results in a memory leak condition. An attacker can exploit this vulnerability by sending standard HTTP requests to the server, triggering the handler to retain memory indefinitely, potentially leading to resource exhaustion and denial of service (DoS). The vulnerability does not affect confidentiality or integrity, as it does not allow data disclosure or modification. No authentication or user interaction is required for exploitation, and the attack surface is limited to servers with the learning-push handler enabled and maxAge unconfigured. Overwriting the maxAge configuration to a valid value mitigates the vulnerability by ensuring proper memory release. There are no known exploits in the wild, and no patches or updates have been linked yet. The CVSS v3.1 base score is 5.3, reflecting a medium severity primarily due to the impact on availability and ease of exploitation over the network without privileges.

The primary impact of CVE-2024-3653 is on the availability of affected Undertow servers. Exploitation can cause a memory leak that, over time, may exhaust server resources, leading to degraded performance or denial of service. This can disrupt web services relying on Undertow, affecting business continuity and user experience. Since the vulnerability does not compromise confidentiality or integrity, the risk of data breaches or unauthorized data modification is minimal. However, organizations running Undertow with the learning-push handler enabled and default maxAge settings are at risk of service outages, which can have cascading effects on dependent applications and services. The ease of exploitation without authentication increases the threat level, especially in environments exposed to the internet. The absence of known exploits suggests limited current active targeting, but the vulnerability's nature means it could be leveraged in denial-of-service campaigns if weaponized.

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, disabling this handler entirely is the most effective mitigation. If the handler must be enabled, explicitly configure the maxAge parameter to a valid positive value to ensure memory is released appropriately after the effective lifetime. Regularly monitor server memory usage for abnormal patterns that could indicate exploitation attempts. Additionally, apply any forthcoming patches or updates from Undertow or related vendors promptly once available. Network-level protections such as rate limiting and web application firewalls can help reduce the risk of exploitation by limiting the volume of malicious HTTP requests. Finally, maintain up-to-date inventory and configuration management to quickly identify and remediate vulnerable server instances.