CVE-2025-52434 is a concurrency vulnerability classified under CWE-362 (Race Condition) affecting the Apache Tomcat server when using the APR/Native connector. The issue manifests during concurrent execution involving shared resources without proper synchronization, specifically triggered by client-initiated closures of HTTP/2 connections. This improper synchronization can lead to unpredictable behavior in the server, primarily resulting in denial of service conditions due to resource conflicts or crashes. The vulnerability affects Apache Tomcat versions from 9.0.0.M1 through 9.0.106 and also older 8.5.x versions up to 8.5.100, including some end-of-life versions. The flaw does not impact confidentiality or integrity but severely affects availability. The CVSS v3.1 score is 7.5 (High), reflecting network attack vector, low attack complexity, no privileges required, no user interaction, and an impact limited to availability. The vulnerability was publicly disclosed on July 10, 2025, with no known exploits in the wild at the time. The recommended remediation is upgrading to Apache Tomcat 9.0.107, where the race condition has been resolved. Organizations using the APR/Native connector with HTTP/2 should prioritize this upgrade to avoid potential service disruptions.

For European organizations, this vulnerability poses a significant risk to the availability of web services hosted on Apache Tomcat servers using the APR/Native connector with HTTP/2 enabled. Denial of service conditions could disrupt critical business applications, customer-facing portals, and internal services, leading to operational downtime and potential financial losses. Sectors such as finance, healthcare, government, and telecommunications, which often rely on Apache Tomcat for scalable web applications, may experience service interruptions affecting end-users and compliance with service-level agreements. Since the vulnerability can be exploited remotely without authentication or user interaction, attackers could launch denial of service attacks at scale, potentially targeting high-profile organizations or critical infrastructure. The lack of confidentiality or integrity impact reduces the risk of data breaches but does not mitigate the operational impact of service outages. The absence of known exploits in the wild currently lowers immediate risk but does not preclude future exploitation, especially given the vulnerability's ease of exploitation and high severity.

1. Upgrade affected Apache Tomcat instances to version 9.0.107 or later, where the race condition vulnerability has been fixed. 2. If immediate upgrade is not feasible, consider disabling the APR/Native connector or HTTP/2 support temporarily to mitigate the risk, understanding this may impact performance or functionality. 3. Implement robust monitoring and alerting for unusual HTTP/2 connection closures or server crashes that could indicate exploitation attempts. 4. Employ network-level protections such as rate limiting and web application firewalls (WAFs) to detect and block suspicious traffic patterns targeting HTTP/2 endpoints. 5. Conduct thorough testing of Tomcat configurations in staging environments to ensure no residual concurrency issues remain post-patching. 6. Maintain an inventory of all Apache Tomcat deployments across the organization to ensure no vulnerable instances remain unpatched. 7. Engage with vendors or managed service providers to confirm that hosted or cloud-based Tomcat services are updated accordingly. 8. Review and update incident response plans to include scenarios involving denial of service attacks exploiting this vulnerability.