CVE-2026-59919

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.

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

// HAProxyMessageEncoder.java:63-77
private static void encodeV1(HAProxyMessage msg, ByteBuf out) {
    out.writeBytes(TEXT_PREFIX);                                    // "PROXY "
    out.writeByte((byte) ' ');
    out.writeCharSequence(msg.proxiedProtocol().name(), US_ASCII); // "UNIX_STREAM"
    out.writeByte((byte) ' ');
    out.writeCharSequence(msg.sourceAddress(), US_ASCII);           // <-- NO CRLF CHECK
    out.writeByte((byte) ' ');
    out.writeCharSequence(msg.destinationAddress(), US_ASCII);      // <-- NO CRLF CHECK
    out.writeByte((byte) ' ');
    // ...
    out.writeByte((byte) '\r');
    out.writeByte((byte) '\n');
}

Root Cause — Insufficient Address Validation

// HAProxyMessage.java:428-442
private static void checkAddress(String address, AddressFamily addrFamily) {
    switch (addrFamily) {
        case AF_UNIX:
            ObjectUtil.checkNotNull(address, "address");
            if (address.getBytes(CharsetUtil.US_ASCII).length > 108) {
                throw new IllegalArgumentException("invalid AF_UNIX address: " + address);
            }
            return;  // ONLY checks length <= 108, NO CRLF validation!
        case AF_IPv4:
            if (!NetUtil.isValidIpV4Address(address)) { ... }  // Format check blocks CRLF
        case AF_IPv6:
            if (!NetUtil.isValidIpV6Address(address)) { ... }  // Format check blocks CRLF
    }
}

IPv4 and IPv6 addresses are validated against format rules that implicitly reject CRLF. But AF_UNIX addresses only check length <= 108 — any characters including CRLF are accepted.

4. Exploitability Prerequisites

This vulnerability is exploitable when:

1. An application uses Netty's HAProxyMessageEncoder to construct HAProxy V1 protocol headers
2. AF_UNIX (UNIX_STREAM or UNIX_DGRAM) addresses contain user-controlled input
3. The encoded PROXY header is sent to a downstream server or load balancer

Affected use cases:

• PROXY protocol relays that construct AF_UNIX messages from upstream data
• Load balancer integrations where socket paths come from configuration or external sources
• Multi-tenant proxies that dynamically construct PROXY headers

5. Attack Scenario

Client IP Spoofing via Second PROXY Line Injection

String maliciousAddr = "/var/run/app.sock\r\nPROXY TCP4 10.0.0.1 10.0.0.2 1234 80";

HAProxyMessage msg = new HAProxyMessage(
    HAProxyProtocolVersion.V1,
    HAProxyCommand.PROXY,
    HAProxyProxiedProtocol.UNIX_STREAM,
    maliciousAddr,                    // CRLF-injected source address
    "/var/run/dest.sock",
…

A client might overload the server by issue frequent RST frames. This can cause a massive amount of load on the remote system and so cause a DDOS attack.

Impact

This is a DDOS attack, any http2 server is affected and so you should update as soon as possible.

Patches

This is patched in version 4.1.100.Final.

Workarounds

A user can limit the amount of RST frames that are accepted per connection over a timeframe manually using either an own Http2FrameListener implementation or an ChannelInboundHandler implementation (depending which http2 API is used).

References

• https://www.cve.org/CVERecord?id=CVE-2023-44487
• https://blog.cloudflare.com/technical-breakdown-http2-rapid-reset-ddos-attack/
• https://cloud.google.com/blog/products/identity-security/google-cloud-mitigated-largest-ddos-attack-peaking-above-398-million-rps/

Red Hat Lightwell has released io.netty:netty-codec-haproxy 4.1.100.Final-rhlw-00001 with backported fixes for CVE-2026-44893, CVE-2026-48059, CVE-2026-55851, and CVE-2026-59919.

CVE-2026-44893: Netty: HAProxy SSL TLV parsing leaks retained slice on invalid TLV length

CVE-2026-48059: Netty HAProxy: Unbalanced Reference Count in Nested PP2_TYPE_SSL TLV Parsing Leads to Memory Exhaustion

CVE-2026-55851: Netty codec-haproxy: Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbounded Memory Exhaustion

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

This patched artifact is a drop-in replacement for io.netty:netty-codec-haproxy 4.1.100.Final from Maven Central.

Root has patched GHSA-xpw8-rcwv-8f8p in the io.root.io.netty:netty-codec-http2 package for Root:Maven. Multiple fixed versions available.

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.

TuxCare rebuilt 47 io.netty packages to address 23 CVEs. Fixed in 4.1.135.Final-tuxcare.1.

TuxCare rebuilt 47 io.netty packages to address 23 CVEs. Fixed in 4.1.130.Final-tuxcare.3.

TuxCare rebuilt 47 io.netty packages to address 59 CVEs. Fixed in 4.1.122.Final-tuxcare.2.

TuxCare rebuilt 47 io.netty packages to address 60 CVEs. Fixed in 4.1.119.Final-tuxcare.1.

TuxCare rebuilt 47 io.netty packages to address 41 CVEs. Fixed in 4.1.112.Final-tuxcare.6.

TuxCare rebuilt 47 io.netty packages to address 62 CVEs. Fixed in 4.1.111.Final-tuxcare.1.

TuxCare rebuilt 47 io.netty packages to address 48 CVEs. Fixed in 4.1.117.Final-tuxcare.3.

TuxCare rebuilt 47 io.netty packages to address 61 CVEs. Fixed in 4.1.108.Final-tuxcare.1.

TuxCare rebuilt 47 io.netty packages to address 61 CVEs. Fixed in 4.1.107.Final-tuxcare.1.

TuxCare rebuilt 47 io.netty packages to address 62 CVEs. Fixed in 4.1.94.Final-tuxcare.1.

TuxCare rebuilt 46 io.netty packages to address 22 CVEs. Fixed in 4.1.79.Final-tuxcare.4.

These are all security issues fixed in the netty-4.1.136-1.1 package on the GA media of openSUSE Tumbleweed.

This update for netty, netty-tcnative fixes the following issues:

Upgrade netty to upstream version 4.1.136 and netty-tcnative to version 2.0.80 Final.

Security issues fixed

• CVE-2026-44891: memory exhaustion in io.netty:netty-codec-stomp (bsc#1271435).
• CVE-2026-55831: resource exhaustion/DoS in io.netty:netty-codec-http (bsc#1271960).
• CVE-2026-55833: zip bomb in io.netty:netty-codec-http (bsc#1271961).
• CVE-2026-55851: memory exhaustion in io.netty:netty-codec-haproxy (bsc#1272253).
• CVE-2026-56745: memory exhaustion in io.netty:netty-codec-http (bsc#1272254).
• CVE-2026-56746: improper access control in io.netty:netty-codec-http (CORS) (bsc#1272255).
• CVE-2026-56817: insecure defaults in XML parsing in io.netty:netty-codec-xml (bsc#1272257).
• CVE-2026-56818: memory leak in io.netty:netty-codec-redis (bsc#1272603).
• CVE-2026-56819: memory leak in io.netty:netty-codec-http2 (bsc#1272258).
• CVE-2026-56820: improper certificate validation in io.netty:netty-handler-ssl-ocsp (bsc#1272259).
• CVE-2026-56821: improper certificate revocation check in io.netty:netty-handler-ssl-ocsp (bsc#1272299).
• CVE-2026-56822: time-of-check/time-of-use in io.netty:netty-handler-ssl-ocsp (bsc#1272300).
• CVE-2026-59898: protocol version confusion in io.netty:netty-codec-http (websocket) (bsc#1272302).
• CVE-2026-59899: memory exhaustion in io.netty:netty-codec-http (bsc#1272301).
• CVE-2026-59900: improper header neutralization in io.netty:netty-codec-http2 (bsc#1272303).
• CVE-2026-59901: infinite loop in io.netty:netty-codec-compression (bzip2) (bsc#1272304).
• CVE-2026-59919: improper CR/LF neutralization in io.netty:netty-codec-haproxy (bsc#1272305).
• CVE-2026-59920: improper CR/LF neutrolization in io.netty:netty-codec-stomp (bsc#1272306).
• CVE-2026-59921: improper CR/LF neutralization in io.netty:netty-codec-http (multipart) (bsc#1272307).
• Memory leak in io.netty:netty-codec-dns (bsc#1272519).
• Uncontrolled resource consumption in io.netty:netty-codec-xml (bsc#1272518).

Other updates and bugfixes:

• Upgrade to upstream version 4.1.136:
  • SingleThreadEventExecutor: document Throwable safety contract on run()
  • Make HTTP/2 frame hashCode consistent with equals
  • Add BlockHound exception for DnsQueryIdSpace (#16896)
  • FlowControlHandler: Fix autoRead behavior
  • Fix incorrect bounds in error message of HpackDecoder.setMaxHeaderListSize
  • MQTT: Fix MQTT decoder size check after variable header replay
  • MQTT: Make the decodeProperties early-REPLAY check actually fire
  • Reject control characters at the boundary of HTTP method names (#16723)
  • Update to latest tcnative release
  • Fix HTTP 2 PUSH_PROMISE stream association validation
  • Fix GZIP FEXTRA extra-field handling in JdkZlibDecoder
  • Add opt-in validation of mandatory pseudo-header fields for HTTP/2
  • Strictly validate MQTT UTF-8 Encoded String (#16939)
  • Stop DateFormatter trailing token from running past the parse end
  • IpFilter: Deprecate constructor which use accept by default
  • Add RFC 10008 QUERY Method support (#16966)
  • Correctly release and fail queued traffic-shaping writes on close (#16959)
  • FlowControlHandler: respect auto-read when toggled while dequeueing
  • IdleStateHandler: reset firstWriter/ReaderIdleEvent in resetWriteTimeout/resetReadTimeout (#16982)
  • Fix typo in AbstractSniHandler Javadoc
  • Reconcile AbstractCoalescingBufferQueue readableBytes when it drains, and fail stuck HTTP/2 streams instead of spinning empty DATA frames
  • Reject control characters at the boundary of the HTTP version token (#16971)
  • Reset UTF-8 decode state on CR in StompSubframeDecoder
  • HTTP2: Pass the correct number of arguments when logging goaway
  • FastLz: Guard decompression against truncated input (#17000)
  • Fix propagation of startTls for client SslContext handler
  • Reject non-token characters in HTTP/2 header names +…