Medium [CVE-2026-59919] Improper CR/LF neutralization in netty-codec-haproxy

Netty is an asynchronous, event-driven network application framework.

In versions prior to 4.1.136.Final and 4.2.16.Final, Netty's HAProxy encoder ( HAProxyMessageEncoder ) writes AF_UNIX source and destination socket addresses into the HAProxy V1 text protocol without validating them for CRLF characters, so an attacker who controls an AF_UNIX address can inject \r\n sequences and split the single PROXY header into multiple lines.

This is possible because the V1 protocol uses CRLF as its line terminator and, unlike IPv4/IPv6 addresses whose format checks implicitly reject CRLF, AF_UNIX addresses are only validated for length (up to 108 bytes), allowing a forged second PROXY header line that spoofs the client source/destination IP to a downstream server or load balancer.

A flaw was found in the netty-codec-haproxy component, part of the Netty network application framework. This vulnerability allows a remote attacker to perform protocol-level injection attacks by crafting malformed HAProxy protocol frames that contain embedded carriage return (CR) and line feed (LF) sequences.

This can lead to the injection of arbitrary content, potentially disrupting network communication or enabling further attacks. This Moderate flaw in `netty-codec-haproxy` allows for protocol-level injection attacks due to improper neutralization of CR/LF sequences.