CVE-2026-59919 — Netty: HAProxy V1 Protocol CRLF Injection via AF_UNIX Address

Affected: netty

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. The issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

GHSA-wh89-7897-x99h — Netty: HAProxy V1 Protocol CRLF Injection via AF_UNIX Address

Affected: Maven: io.netty:netty-codec-haproxy

# Security Vulnerability Report: HAProxy V1 Protocol CRLF Injection via AF_UNIX Address in Netty

## 1. Vulnerability Summary

| Field | Value | |-------|-------| | **Product** | Netty | | **Version** | 4.2.12.Final (and all prior versions with codec-haproxy) | | **Component** | `io.netty.handler.codec.haproxy.HAProxyMessageEncoder` | | **Vulnerability Type** | CWE-93: Improper Neutralization of CRLF Sequences | | **Impact** | HAProxy PROXY Protocol Injection / Client IP Spoofing | | **CVSS 3.1 Score** | **7.5 (High)** | | **CVSS 3.1 Vector** | `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N` |

## 2. Affected Components

- `io.netty.handler.codec.haproxy.HAProxyMessageEncoder` — `encodeV1()` method (lines 63-77): writes `sourceAddress` and `destinationAddress` directly to output without CRLF validation - `io.netty.handler.codec.haproxy.HAProxyMessage` — constructor `checkAddress()` validates IPv4/IPv6 format but **only checks length for AF_UNIX** (line 439)

## 3. Vulnerability Description

Netty's HAProxy protocol encoder writes AF_UNIX socket addresses directly into the HAProxy V1 text protocol format **without validating for CRLF characters**. The V1 protocol uses CRLF (`\r\n`) as the line terminator, so CRLF characters in an address split the single PROXY header line into multiple lines, effectively injecting a second PROXY protocol header.

### Root Cause — Encoder

```java // HAProxyMessageEncoder.java:63-77 private static void encodeV1(HAProxyMessage msg, ByteBuf out)…

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CVE-2026-59919 — Netty: HAProxy V1 Protocol CRLF Injection via AF_UNIX Address

GHSA-wh89-7897-x99h — Netty: HAProxy V1 Protocol CRLF Injection via AF_UNIX Address