Netty up to 4.1.137.Final/4.2.17.Final Transfer-Encoding request smuggling

Summaryinfo

A vulnerability classified as problematic has been found in Netty up to 4.1.137.Final/4.2.17.Final. The affected element is an unknown function of the component Transfer-Encoding. Performing a manipulation results in request smuggling. This vulnerability is reported as CVE-2026-89044. The attack is possible to be carried out remotely. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Netty up to 4.1.137.Final/4.2.17.Final. This affects some unknown processing of the component Transfer-Encoding. The manipulation with an unknown input leads to a request smuggling vulnerability. CWE is classifying the issue as 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. This is going to have an impact on integrity. The summary by CVE is:

Netty versions 4.1.133.Final through 4.1.137.Final and 4.2.13.Final through 4.2.17.Final fail to properly validate the final transfer coding in the Transfer-Encoding header, allowing attackers to smuggle requests by using malformed encoding declarations. Attackers can split Transfer-Encoding headers across multiple lines or use values like 'chunked, xchunked' to bypass validation and decode messages as chunked when the final coding is not chunked, enabling request smuggling attacks.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-89044 since 09/10/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available.

Upgrading to version 4.1.138.Final or 4.2.18.Final eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Name

• Netty

Version

• 4.1.137.Final
• 4.2.17.Final

Website

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

CPE 2.3info

• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Discussion