CVE-2026-59919 Netty: HAProxy V1 Protocol CRLF Injection via AF_UNIX Address
Attackers can inject CRLF sequences into HAProxy V1 headers via AF_UNIX addresses, spoofing client IPs to downstream servers.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-59919?
CVE-2026-59919 is a medium-severity vulnerability in Netty Netty, published on 29 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-93
Which versions are affected by CVE-2026-59919?
4 open source packages ship an affected version, including io.netty:netty-codec-haproxy. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
io.netty:netty-codec-haproxy Maven | All versions | 4.1.136.Final |
io.netty:netty-codec-haproxy Maven | All versions | 4.1.136.Final |
io.netty:netty-codec-haproxy Maven | From 4.2.0.Final | 4.2.16.Final |
io.netty:netty-codec-haproxy Maven | From 4.2.0.Final | 4.2.16.Final |
Products include Netty Netty.
How do I fix CVE-2026-59919?
Upgrade io.netty:netty-codec-haproxy to a fixed version for your release line: 4.1.136.Final or 4.2.16.Final.
Is CVE-2026-59919 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59919 exists.
Other vulnerabilities in Netty Netty
- CVE-2026-75595 Netty: SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext
- CVE-2026-75596 Netty: Fragmented ClientHello records trigger quadratic pre-handshake reassembly in default SNI parsing
- CVE-2026-59901 Netty Bzip2Decoder: Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang
- CVE-2026-55851 Netty codec-haproxy: Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbounded Memory Exhaustion
- CVE-2026-56745 Netty SpdyHttpDecoder: ByteBuf Reference Leak on RST_STREAM Leads to Native Memory Exhaustion
Sources
Also known as CLEANSTART-2026-DB56545, CLEANSTART-2026-NC41949, DEBIAN-CVE-2026-59919, ECHO-970b-879f-6b93, GHSA-wh89-7897-x99h, MINI-29rj-fwgw-2q93 and 38 more.