CVE-2026-59919

Analyzed Analyzed - Analysis Complete

CRLF Injection in Netty HAProxyMessageEncoder

Publication date: 2026-07-29

Last updated on: 2026-08-06

Assigner: GitHub, Inc.

Description

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.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-07-29

Last Modified

2026-08-06

Generated

2026-08-19

AI Q&A

2026-07-30

EPSS Evaluated

2026-08-18

NVD

CVE-2026-59919

Affected Vendors & Products

Vendor	Product	Version / Range
netty	netty	to 4.1.136 (exc)
netty	netty	From 4.2.0 (inc) to 4.2.16 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-93	The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs.

Attack-Flow Graph

Executive Summary

Netty's HAProxy encoder writes AF_UNIX socket addresses into the HAProxy V1 protocol without checking for CRLF characters. An attacker controlling an AF_UNIX address can inject CRLF sequences to split the PROXY header into multiple lines, allowing header injection. This exploits the protocol's CRLF line terminators and bypasses validation due to AF_UNIX's length-only checks.

Detection Guidance

Detecting this vulnerability requires checking the Netty version in use. If you are running a version prior to 4.1.136.Final or 4.2.16.Final, the system is vulnerable. Commands like 'find / -name "netty-*.jar" 2>/dev/null' or checking dependency files (e.g., Maven's pom.xml, Gradle's build.gradle) can help identify the installed version.

Impact Analysis

An attacker could spoof client source/destination IP addresses in the PROXY header, potentially bypassing security controls or redirecting traffic. This may lead to unauthorized access, data leaks, or manipulation of downstream servers or load balancers using Netty.

Compliance Impact

This vulnerability could potentially impact compliance with standards like GDPR and HIPAA by enabling header injection attacks that manipulate network traffic. If exploited, it may allow attackers to spoof client source/destination information, potentially bypassing security controls or logging mechanisms required for regulatory compliance.

Mitigation Strategies

Upgrade Netty to version 4.1.136.Final or later for the 4.1.x branch, or 4.2.16.Final or later for the 4.2.x branch. If upgrading is not immediately possible, consider disabling the HAProxyMessageEncoder or restricting network access to trusted sources to reduce exposure.

Hi! I’m here to help you understand CVE-2026-59919. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70