Medium · published December 16, 2025
Netty is an asynchronous, event-driven network application framework. In versions prior to 4.1.129.Final and 4.2.8.Final, the `io.netty.handler.codec.http.HttpRequestEncoder` has a CRLF injection with the request URI when constructing a request. This leads to request smuggling when `HttpRequestEncoder` is used without proper sanitization of the URI. Any application / framework using `HttpRequestEncoder` can be subject to be abused to perform request smuggling using CRLF injection. Versions 4.1.129.Final and 4.2.8.Final fix the issue.
| Product | Versions | Fixed in |
|---|---|---|
| netty/netty | < 4.1.129 | 4.1.129 |
| netty/netty | ≥ 4.2.0, < 4.2.8 | 4.2.8 |