HTTP Request Smuggling Affecting netty package, versions <1:4.1.48-16ubuntu0.1~esm2


Severity

Recommended
medium

Based on Ubuntu security rating.

Threat Intelligence

EPSS
0.02% (6th percentile)

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  • Snyk IDSNYK-UBUNTU2604-NETTY-16780832
  • published3 Jun 2026
  • disclosed13 May 2026

Introduced: 13 May 2026

CVE-2026-42581  (opens in a new tab)
CWE-444  (opens in a new tab)

How to fix?

Upgrade Ubuntu:26.04 netty to version 1:4.1.48-16ubuntu0.1~esm2 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream netty package and not the netty package as distributed by Ubuntu. See How to fix? for Ubuntu:26.04 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1