Netty up to 1.0/1.1/4.1.133.Final/4.2.13.Final HTTPObjectDecoder request smuggling

Summaryinfo

A vulnerability identified as problematic has been detected in Netty up to 1.0/1.1/4.1.133.Final/4.2.13.Final. This affects an unknown function of the component HTTPObjectDecoder. The manipulation leads to request smuggling. This vulnerability is documented as CVE-2026-42581. The attack can be initiated remotely. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Netty up to 1.0/1.1/4.1.133.Final/4.2.13.Final. This issue affects some unknown functionality of the component HTTPObjectDecoder. The manipulation with an unknown input leads to a request smuggling vulnerability. Using CWE to declare the problem leads to 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. Impacted is integrity. The summary by CVE is:

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, HttpObjectDecoder strips a conflicting Content-Length header when a request carries both Transfer-Encoding: chunked and Content-Length, but only for HTTP/1.1 messages. The guard is absent for HTTP/1.0. An attacker that sends an HTTP/1.0 request with both headers causes Netty to decode the body as chunked while leaving Content-Length intact in the forwarded HttpMessage. Any downstream proxy or handler that trusts Content-Length over Transfer-Encoding will disagree on message boundaries, enabling request smuggling. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-42581 since 04/28/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 314896 (Linux Distros Unpatched Vulnerability : CVE-2026-42581), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 4.1.133.Final or 4.2.13.Final eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (314896). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Name

• Netty

Version

• 1.0
• 1.1
• 4.1.133.Final
• 4.2.13.Final

Website

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

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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