CVE-2025-52434: Apache Tomcat Race Condition Vulnerability

CVE-2025-52434 Overview

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') vulnerability in Apache Tomcat when using the APR/Native connector. This was particularly noticeable with client-initiated closes of HTTP/2 connections.

This issue affects Apache Tomcat from version 9.0.0.M1 through 9.0.106 and EOL versions 8.5.0 through 8.5.100. Users are recommended to upgrade to version 9.0.107, which fixes the issue.

Critical Impact

Affects all HTTP/2 connections in specific Tomcat versions, leading to potential denial of service.

Affected Products

• Apache Tomcat 9.0.0.M1 through 9.0.106
• Apache Tomcat 8.5.0 through 8.5.100

Discovery Timeline

• 2025-07-10 - CVE-2025-52434 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2025-52434

Vulnerability Analysis

A race condition occurs in the Apache Tomcat server when multiple threads access shared resources without proper synchronization, specifically if a client initiates closure of HTTP/2 connections while using the APR/Native connector. This behavior can cause unexpected application state and may result in a denial of service.

Root Cause

Improper synchronization of shared resources when handling HTTP/2 connections using the APR/Native connector.

Attack Vector

Network-based attacks can be initiated by interacting with HTTP/2 connections, causing race conditions that lead to denial of service.

// Example exploitation code (sanitized)
void exploit(Http2Connection connection) {
    // Create multiple threads that initiate closure requests
    Thread t1 = new Thread(() -> connection.close());
    Thread t2 = new Thread(() -> connection.close());
    t1.start();
    t2.start();
}

Detection Methods for CVE-2025-52434

Indicators of Compromise

• Elevated error rates in Tomcat logs
• HTTP/2 connection resets
• Performance degradation

Detection Strategies

Use SentinelOne's behavioral AI to detect anomalies in HTTP/2 connection handling and identify race conditions by monitoring anomalous thread activity.

Monitoring Recommendations

Regularly inspect Tomcat logs for unusual connection resets and error patterns. Monitor system performance metrics for signs of denial of service.

How to Mitigate CVE-2025-52434

Immediate Actions Required

• Upgrade to Apache Tomcat version 9.0.107 immediately.
• Implement application whitelisting to prevent unauthorized modifications.
• Utilize SentinelOne's runtime protection to monitor and block attempts to exploit vulnerable paths.

Patch Information

Upgrade to Apache Tomcat version 9.0.107 as detailed in the vendor advisory.

Workarounds

Disable the APR/Native connector if HTTP/2 functionality is not necessary until the patch can be applied.

# Configuration example to disable APR/Native connector
<Connector 
    protocol="org.apache.coyote.http11.Http11Nio2Protocol" 
    maxThreads="150" 
    SSLEnabled="true"
    ... 
/>