CVE-2025-58056 Netty is vulnerable to request smuggling due to incorrect parsing of chunk extensions
Attackers can perform HTTP request smuggling by exploiting incorrect chunk extension parsing in the Netty library, bypassing security controls.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-58056?
CVE-2025-58056 is a low-severity vulnerability in Netty Netty, published on 3 Sep 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Netty is an asynchronous event-driven network application framework for development of maintainable high performance protocol servers and clients. In versions 4.1.124.Final, and 4.2.0.Alpha3 through 4.2.4.Final, Netty incorrectly accepts standalone newline characters (LF) as a chunk-size line terminator, regardless of a preceding carriage return (CR), instead of requiring CRLF per HTTP/1.1 standards. When combined with reverse proxies that parse LF differently (treating it as part of the chunk extension), attackers can craft requests that the proxy sees as one request but Netty processes as two, enabling request smuggling attacks. This is fixed in versions 4.1.125.Final and 4.2.5.Final.
Weakness: CWE-444
Which versions are affected by CVE-2025-58056?
4 open source packages ship an affected version, including io.netty:netty-codec-http. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
io.netty:netty-codec-http Maven | All versions | 4.1.125.Final |
io.netty:netty-codec-http Maven | All versions | 4.1.125.Final |
io.netty:netty-codec-http Maven | From 4.2.0.Alpha1 | 4.2.5.Final |
io.netty:netty-codec-http Maven | From 4.2.0.Alpha1 | 4.2.5.Final |
Products include Netty Netty.
How do I fix CVE-2025-58056?
Upgrade io.netty:netty-codec-http to a fixed version for your release line: 4.1.125.Final or 4.2.5.Final.
Is CVE-2025-58056 being exploited?
There is no known exploitation of CVE-2025-58056 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-BY06719, CLEANSTART-2026-DA27362, CLEANSTART-2026-NH27308, CLEANSTART-2026-ZQ44545, CLSA-2026-1776818214, CLSA-2026-1793136168 and 39 more.