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

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-07-29 · updated 2026-08-06
Weakness: CWE-93

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.

Affected products

netty: before 4.1.136; from 4.2.0 before 4.2.16 — fixed in 4.1.136, 4.2.16

How to fix

Upgrade to a fixed version: netty 4.1.136, 4.2.16. Check the vendor advisory for mitigations.

References

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