CVE-2024-5971 is a vulnerability identified in the Undertow web server framework, specifically affecting its handling of HTTP chunked transfer encoding responses when operating under Java 17 with TLSv1.3 enabled. The issue arises because Undertow fails to send the terminating chunk sequence (0\r\n) after the response body has been flushed. Although the response headers and body are transmitted, the absence of this termination causes the client to wait indefinitely for the end of the response. This behavior leads to uncontrolled recursion in resource consumption on the server side, as the server continues to allocate resources waiting for the client to acknowledge the end of the response. The result is a denial of service (DoS) condition, where server resources are exhausted, potentially causing service outages or degraded performance. The vulnerability affects Undertow versions from 0 up to 2.3.0.Alpha1 and is exploitable remotely without any authentication or user interaction, increasing its risk profile. The CVSS v3.1 base score is 7.5 (high), reflecting the network attack vector, low attack complexity, no privileges required, no user interaction, and an impact limited to availability. No known exploits have been reported in the wild yet, but the vulnerability's nature makes it a significant concern for environments relying on Undertow with Java 17 TLSv1.3 configurations.

For European organizations, this vulnerability poses a significant risk to the availability of web services that utilize Undertow with Java 17 TLSv1.3. Public-facing applications, APIs, and internal services relying on this stack could be targeted by attackers to cause denial of service, leading to service disruptions, potential loss of customer trust, and operational downtime. Industries such as finance, healthcare, and government, which often deploy Java-based web servers, may experience critical impacts due to the reliance on continuous availability and stringent service level agreements. Additionally, the uncontrolled resource consumption could lead to increased operational costs and complicate incident response efforts. Given the vulnerability does not affect confidentiality or integrity, the primary concern remains service availability and resilience against DoS attacks.

Organizations should prioritize updating Undertow to a version that addresses CVE-2024-5971 once a patch is released. Until then, practical mitigations include: 1) Temporarily disabling TLSv1.3 if feasible, or reverting to Java versions or TLS configurations not affected by this issue; 2) Implementing rate limiting and connection throttling at the network or application layer to mitigate potential DoS attempts exploiting this flaw; 3) Monitoring server resource utilization and network traffic for abnormal patterns indicative of exploitation attempts; 4) Employing Web Application Firewalls (WAFs) to detect and block malformed or suspicious chunked transfer requests; 5) Reviewing and testing application behavior under chunked transfer scenarios to identify and mitigate any cascading failures; 6) Engaging with Undertow and Java community channels for updates and recommended patches. These steps go beyond generic advice by focusing on configuration adjustments and proactive monitoring tailored to this vulnerability's characteristics.