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 when using the APR/Native connector. The vulnerability arises due to improper synchronization during concurrent execution of shared resources, particularly noticeable when clients initiate HTTP/2 connection closures. This race condition can lead to unexpected behavior in the server, primarily impacting availability. The vulnerability does not affect confidentiality or integrity directly but can cause denial of service conditions by crashing or destabilizing the Tomcat server instance. The flaw is exploitable remotely without authentication or user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). The issue was addressed in Apache Tomcat version 9.0.107, which includes fixes to properly synchronize shared resource access and prevent the race condition. No known exploits are currently reported in the wild, but the ease of exploitation and potential impact on service availability make this a significant threat to organizations relying on affected Tomcat versions with the APR/Native connector enabled.

For European organizations, this vulnerability poses a risk primarily to the availability of web services and applications hosted on Apache Tomcat servers using the APR/Native connector. Many enterprises, government agencies, and service providers in Europe rely on Tomcat for critical web infrastructure. An attacker exploiting this race condition could cause service interruptions or denial of service, impacting business continuity, user experience, and potentially leading to financial losses or reputational damage. Sectors such as finance, healthcare, public administration, and e-commerce, which often deploy Tomcat in their technology stacks, could be particularly affected. Additionally, disruption of public-facing services could have broader societal impacts, especially if critical infrastructure or citizen services are involved. The vulnerability’s remote exploitability without authentication increases the risk profile, making it attractive for opportunistic attackers or automated scanning campaigns targeting vulnerable servers.

European organizations should immediately assess their Apache Tomcat deployments to identify affected versions (9.0.0.M1 through 9.0.106) running with the APR/Native connector enabled. The primary mitigation is to upgrade to Apache Tomcat version 9.0.107 or later, which contains the official fix for this race condition. Where immediate upgrade is not feasible, organizations should consider temporarily disabling the APR/Native connector or switching to the Java NIO connector to mitigate exposure. Network-level protections such as web application firewalls (WAFs) and intrusion prevention systems (IPS) should be configured to detect and block suspicious HTTP/2 connection closure patterns that might trigger the race condition. Additionally, monitoring server logs for abnormal crashes or restarts can help detect exploitation attempts. Implementing robust incident response plans and ensuring backups and failover mechanisms are in place will reduce downtime impact if exploitation occurs. Regular vulnerability scanning and patch management processes should be reinforced to prevent similar issues.