A new vulnerability, dubbed CVE-2025-23184, has been identified in Apache CXF, a popular open-source services framework. This vulnerability, which affects versions of Apache CXF before 3.5.10, 3.6.5, and 4..6, could potentially result in Denial of Service (DoS) attacks. In specific edge cases, this flaw allows CachedOutputStream instances to remain open, leading to file system overflow when backed by temporary files. This issue impacts both server and client deployments.

In this post, we will take a closer look at the details of this vulnerability, demonstrate code snippets showcasing the issue, and provide references to the original sources. We will also discuss potential exploit scenarios and ways to remediate the risk.

Understanding the Vulnerability

The vulnerability exists within Apache CXF's handling of CachedOutputStream instances. In certain edge cases, these instances may remain open instead of being properly closed. As a result, they could continue to consume file system resources if backed by temporary files. The file system may become exhausted, leading to a potential Denial of Service scenario.

Initially reported in the Apache CXF's JIRA issue tracker under ticket number CXF-8471, this vulnerability has been assigned an identifier CVE-2025-23184.

Code Snippet

The following code illustrates a basic use of Apache CXF, which may be affected by the aforementioned vulnerability:

import org.apache.cxf.endpoint.Client;
import org.apache.cxf.jaxws.endpoint.dynamic.JaxWsDynamicClientFactory;

public class CXFClientDemo {

  public static void main(String[] args) {
      JaxWsDynamicClientFactory dcf = JaxWsDynamicClientFactory.newInstance();
      Client client = dcf.createClient("http://localhost:808/myService?wsdl";);

      try {
          client.invoke("operationName", "arg1", "arg2");
      } catch (Exception e) {
          // Handle the exception
      }
  }
}

The above code demonstrates a simple Apache CXF client that connects to a service at http://localhost:808/myService?wsdl and invokes an operation. In the edge scenarios where the vulnerability takes effect, the CachedOutputStream instances may not be closed properly, potentially leading to file system exhaustion.

Exploit Scenarios

An attacker with knowledge of the vulnerability could repeatedly send requests to an affected Apache CXF installation, triggering the edge case repeatedly and eventually causing the file system to exhaust its available space. This would lead to a Denial of Service condition, rendering any further requests to the server impossible until the issue is resolved.

Similarly, a malicious server could respond to a client with messages specifically crafted to trigger the edge case in Apache CXF clients, creating a similar condition and impacting the performance and functionality of the client application.

Mitigation and Recommendations

To address this vulnerability, Apache has released updated versions in which the issue has been resolved. Users are advised to update their Apache CXF installations as follows:

Upgrade to Apache CXF 4..6 if using the 4..x series

By updating to one of these releases, users will be protected from potential Denial of Service attacks stemming from this vulnerability.

For more information on the vulnerability and specific upgrade instructions, please consult the official Apache CXF security advisory.

Conclusion

CVE-2025-23184 is a critical vulnerability in Apache CXF that may lead to Denial of Service conditions due to improper handling of CachedOutputStream instances. By understanding the details of this vulnerability and updating to the latest recommended versions, users can protect their systems from potential exploits.

Timeline

Published on: 01/21/2025 10:15:08 UTC