CVE-2026-44893 Netty: HAProxy SSL TLV parsing leaks retained slice on invalid TLV length
An attacker can cause a memory leak and potential denial of service by sending malformed HAProxy SSL TLV data to applications using the Netty codec.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-44893?
CVE-2026-44893 is a high-severity denial of service vulnerability in Netty Netty, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Netty is a network application framework for development of protocol servers and clients. In netty-codec-haproxy prior to versions 4.1.135.Final and 4.2.15.Final, when decoding a PP2_TYPE_SSL TLV, HAProxyMessage.readNextTLV() first calls `header.retainedSlice(header.readerIndex(), length)` and only then reads the 1-byte client field and 4-byte verify field. If the attacker sets the TLV length below 5, the subsequent readByte/readInt throws IndexOutOfBoundsException. HAProxyMessageDecoder only catches HAProxyProtocolException around this call, so the IOOBE propagates and the retained slice on the pooled cumulation buffer is never released. Versions 4.1.135.Final and 4.2.15.Final patch the issue.
Which versions are affected by CVE-2026-44893?
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 | 4.1.135.Final |
io.netty:netty-codec-haproxy Maven | All versions | 4.1.135.Final |
io.netty:netty-codec-haproxy Maven | From 4.2.0.Final | 4.2.15.Final |
io.netty:netty-codec-haproxy Maven | From 4.2.0.Final | 4.2.15.Final |
Products include Netty Netty.
How do I fix CVE-2026-44893?
Upgrade io.netty:netty-codec-haproxy to a fixed version for your release line: 4.1.135.Final or 4.2.15.Final.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-44893 being exploited?
There is no known exploitation of CVE-2026-44893 in the wild and no public exploit code.
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-RS36042, CLEANSTART-2026-SO96851, CLEANSTART-2026-WP83796, DEBIAN-CVE-2026-44893, ECHO-e271-a55c-dc61, GHSA-cc37-9q2j-3hfv and 29 more.