CVE-2025-25193: Netty Vulnerability in Unsafe Reading of Environment File Could Cause Denial of Service

Netty, an open-source asynchronous, event-driven network application framework, has been found to have a vulnerability in versions up to and including 4.1.118.Final. This vulnerability, identified as CVE-2025-25193, is a result of an unsafe reading of an environment file, which could potentially lead to a denial of service (DoS) attack scenario in Netty applications. This post will detail the specifics of this vulnerability, provide code snippets, and links to original reference materials and commit information.

Background

Netty is widely used for the development of high-performance network applications, providing a robust and flexible framework for handling network traffic in real-time. However, this vulnerability, if exploited, could have severe implications for many applications built upon this popular framework. The issue is closely related to a previous vulnerability, CVE-2024-47535, which was not completely fixed, as it did not consider null-bytes during input size calculations.

Exploit Details

When Netty applications run on Windows, they attempt to load a file that does not exist by default. If an attacker can create a particularly large file that meets these criteria, the Netty application can crash, resulting in a denial of service. This occurs due to the faulty handling of environment file reading, specifically failing to account for null-bytes when calculating input size limits.

Here's a code snippet representing the affected line of code

int maxVar = SystemPropertyUtil.getInt("io.netty.EnvUtil.maxDirectMemory", );

When the commit for the fix to the earlier CVE-2024-47535 was implemented, null-bytes were not considered during input size calculations, resulting in an incomplete fix. The updated patch that addresses this issue can be found in commit d1fbda62d3a47835d3fb35db8bd42ecc205a5386 on GitHub.

Mitigation

To mitigate this vulnerability, developers should update their Netty dependency to version 4.1.119.Final or later.

<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.119.Final</version>
</dependency>

Recommendations

To keep your applications secure, it is essential to keep up-to-date with the latest security patches and updates, especially those concerning widely-used frameworks like Netty. Regularly reviewing the official website, GitHub repository, and security mailing lists for your dependencies can help you stay informed about any new vulnerabilities, exploits, and fixes.

References

- Official Netty Repository on GitHub: https://github.com/netty/netty
- Vulnerable Code Snippet: https://github.com/netty/netty/blob/44726cae01d683c6fd4632d7b6d33bc49b579679/common/src/main/java/io/netty/util/internal/PlatformDependent.java#L192
- Commit Containing Updated Fix: https://github.com/netty/netty/commit/d1fbda62d3a47835d3fb35db8bd42ecc205a5386

Conclusion

The CVE-2025-25193 vulnerability is an important reminder of the need to ensure that our applications and the frameworks they rely upon are secure. It is crucial for organizations to implement robust security practices and maintain up-to-date dependencies to protect themselves from potential threats.

Timeline

Published on: 02/10/2025 22:15:38 UTC
Last modified on: 02/11/2025 16:15:52 UTC