CVE-2025-52434 is a high-severity race condition vulnerability (CWE-362) found in the Apache Tomcat server, specifically affecting versions from 9.0.0.M1 through 9.0.106 and 8.5.0 through 8.5.100, including some older EOL versions. The flaw arises in the APR/Native connector implementation when handling HTTP/2 connections, particularly during client-initiated connection closes. A race condition occurs due to improper synchronization when multiple threads concurrently access shared resources, leading to unpredictable behavior. This can cause denial of service (DoS) conditions by crashing or destabilizing the server, as the vulnerability impacts availability without compromising confidentiality or integrity. The vulnerability requires no authentication or user interaction and can be exploited remotely over the network. The Apache Tomcat project has addressed this issue in version 9.0.107, and users are strongly advised to upgrade to this or later versions to mitigate the risk. No known exploits are currently reported in the wild, but the ease of exploitation and the critical role of Tomcat in web infrastructure make this a significant threat.

For European organizations, this vulnerability poses a substantial risk to the availability of web services relying on Apache Tomcat, especially those using the APR/Native connector with HTTP/2 enabled. Many enterprises, government agencies, and service providers across Europe use Tomcat as a core component of their web application stacks. Exploitation could lead to service outages, disrupting business operations, customer access, and critical public services. Given the high adoption of Tomcat in sectors such as finance, healthcare, and public administration in Europe, the impact could be widespread. Additionally, denial of service incidents could indirectly affect data processing and compliance with regulations like GDPR if service interruptions prevent timely data handling. The lack of confidentiality or integrity impact reduces the risk of data breaches but does not diminish the operational consequences of downtime.

European organizations should prioritize upgrading Apache Tomcat instances to version 9.0.107 or later, which contains the fix for this race condition. For environments where immediate upgrade is not feasible, organizations should consider disabling the APR/Native connector or HTTP/2 support temporarily to reduce exposure. Implementing robust monitoring to detect unusual connection terminations or server instability can help identify exploitation attempts early. Network-level protections such as rate limiting and web application firewalls (WAFs) configured to detect abnormal HTTP/2 traffic patterns may also mitigate attack surface. Additionally, organizations should review and test their incident response plans to handle potential denial of service events. Regular patch management processes must be enforced to ensure timely application of security updates.