Netty prior 4.1.125.Final/4.2.5.Final request smuggling

Summaryinfo

A vulnerability, which was classified as critical, has been found in Netty. This vulnerability affects unknown code. This manipulation causes request smuggling. This vulnerability is registered as CVE-2025-58056. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Netty. Affected by this vulnerability is an unknown functionality. The manipulation with an unknown input leads to a request smuggling vulnerability. The CWE definition for the vulnerability is CWE-444. The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. As an impact it is known to affect integrity, and availability. The summary by CVE is:

Netty is an asynchronous event-driven network application framework for development of maintainable high performance protocol servers and clients. In versions 4.1.124.Final, and 4.2.0.Alpha3 through 4.2.4.Final, Netty incorrectly accepts standalone newline characters (LF) as a chunk-size line terminator, regardless of a preceding carriage return (CR), instead of requiring CRLF per HTTP/1.1 standards. When combined with reverse proxies that parse LF differently (treating it as part of the chunk extension), attackers can craft requests that the proxy sees as one request but Netty processes as two, enabling request smuggling attacks. This is fixed in versions 4.1.125.Final and 4.2.5.Final.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2025-58056 since 08/22/2025. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. The technical details are unknown and an exploit is not publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 261590 (Linux Distros Unpatched Vulnerability : CVE-2025-58056), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 4.1.125.Final or 4.2.5.Final eliminates this vulnerability. Applying the patch edb55fd8e0a3bcbd85881e423464f585183d1284 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (261590) and CERT Bund (WID-SEC-2025-2301). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Red Hat Enterprise Linux
• HCL Commerce
• Atlassian Jira
• Dell Secure Connect Gateway

Productinfo

Name

• Netty

License

• open-source

Website

• Product: https://github.com/netty/netty/

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