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.
Problem types
CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Product status
<= 4.1.124.Final, < 4.1.125.Final
References
github.com/.../netty/security/advisories/GHSA-fghv-69vj-qj49
github.com/JLLeitschuh/unCVEed/issues/1
github.com/netty/netty/issues/15522
github.com/netty/netty/pull/15611
github.com/...ommit/edb55fd8e0a3bcbd85881e423464f585183d1284
datatracker.ietf.org/doc/html/rfc9112
w4ke.info/2025/06/18/funky-chunks.html