Netty, a popular asynchronous and event-driven network application framework, suffers from a critical vulnerability labeled CVE-2025-24970, which affects versions 4.1.91.Final through 4.1.117.Final. The issue arises due to Netty's SslHandler not adequately validating specially crafted packets in all cases. This ultimately results in a native crash. Thankfully, the vulnerability has been patched in version 4.1.118.Final.

In this post, we'll delve into the details of the vulnerability, including examining some code snippets, providing links to original references, and discussing exploit details.

Vulnerability Details

The Netty framework provides SslHandler, a crucial component that manages SSL/TLS encryption for network connections. It is prone to a vulnerability when dealing with specific packets. The SslHandler implementation does not correctly handle packet validation in some instances, which eventually causes a native crash.

A threat actor can exploit this vulnerability and potentially disrupt network applications by sending specially crafted packets. This can result in denial-of-service attacks or other potential security hazards.

Code Snippet

To demonstrate the issue, let's examine the following code snippet from the vulnerable SslHandler implementation:

ByteBuf buf = Unpooled.wrappedBuffer(packet);
SslHandler sslHandler = ...;
sslHandler.channelRead(ctx, buf);

In this example, an attacker could potentially send a malicious packet, causing the SslHandler to crash the application.

Patch and Workarounds

Fortunately, the vulnerability has been patched in Netty version 4.1.118.Final. We highly recommend updating to this version to mitigate the risk of native crashes.

Disable the usage of native SSLEngine

System.setProperty("io.netty.handler.ssl.noOpenSsl", "true");

2. Manually modify the vulnerable code in your Netty implementation. While this may not be the ideal solution, it can serve as a temporary fix until you can update to the patched version.

For more information on the CVE-2025-24970 vulnerability, you can refer to the following resources

1. Netty's official GitHub repository, which contains the patched version of the framework: https://github.com/netty/netty

2. The CVE database, where the vulnerability has been documented: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2025-24970

3. The National Vulnerability Database (NVD) entry with more details on the exploit: https://nvd.nist.gov/vuln/detail/2025-24970

Conclusion

Network application frameworks, such as Netty, that deal with encryption can be prone to vulnerabilities. In the case of CVE-2025-24970, an issue with SslHandler packet validation lead to a native crash in specific versions of the framework, posing a security risk. To mitigate the vulnerability, it is crucial to update to the patched version 4.1.118.Final or implement one of the proposed workarounds. Stay vigilant and keep your software up-to-date to avoid potential threats in the future.

Timeline

Published on: 02/10/2025 22:15:38 UTC
Last modified on: 02/11/2025 16:15:51 UTC