GHSA-g2xc-35jw-c63p
Vulnerability from github
Published
2019-12-20 23:04
Modified
2022-04-25 23:07
Severity ?
7.1 (High) - CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N
Summary
HTTP Request Smuggling: Invalid Transfer-Encoding in Waitress
Details

Impact

Waitress would parse the Transfer-Encoding header and only look for a single string value, if that value was not chunked it would fall through and use the Content-Length header instead.

According to the HTTP standard Transfer-Encoding should be a comma separated list, with the inner-most encoding first, followed by any further transfer codings, ending with chunked.

Requests sent with:

Transfer-Encoding: gzip, chunked

Would incorrectly get ignored, and the request would use a Content-Length header instead to determine the body size of the HTTP message.

This could allow for Waitress to treat a single request as multiple requests in the case of HTTP pipelining.

Patches

This issue is fixed in Waitress 1.4.0. This brings a range of changes to harden Waitress against potential HTTP request confusions, and may change the behaviour of Waitress behind non-conformist proxies.

Waitress will now return a 501 Not Implemented error if the Transfer-Encoding is not chunked or contains multiple elements. Waitress does not support any transfer codings such as gzip or deflate.

The Pylons Project recommends upgrading as soon as possible, while validating that the changes in Waitress don't cause any changes in behavior.

Workarounds

Various reverse proxies may have protections against sending potentially bad HTTP requests to the backend, and or hardening against potential issues like this. If the reverse proxy doesn't use HTTP/1.1 for connecting to the backend issues are also somewhat mitigated, as HTTP pipelining does not exist in HTTP/1.0 and Waitress will close the connection after every single request (unless the Keep Alive header is explicitly sent... so this is not a fool proof security method).

Issues/more security issues:

  • open an issue at https://github.com/Pylons/waitress/issues (if not sensitive or security related)
  • email the Pylons Security mailing list: pylons-project-security@googlegroups.com (if security related)
Show details on source website

To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "affected_functions": [
          "waitress.parser.HTTPRequestParser.received",
          "waitress.parser.HTTPRequestParser.parse_header",
          "waitress.parser.get_header_lines",
          "waitress.receiver.ChunkedReceiver",
          "waitress.receiver.ChunkedReceiver.received",
          "waitress.utilities.find_double_newline",
          "waitress.utilities.Error"
        ]
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "waitress"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2019-16786"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-444"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2019-12-20T23:01:53Z",
    "nvd_published_at": "2019-12-20T23:15:00Z",
    "severity": "HIGH"
  },
  "details": "### Impact\n\nWaitress would parse the `Transfer-Encoding` header and only look for a single string value, if that value was not `chunked` it would fall through and use the `Content-Length` header instead.\n\nAccording to the HTTP standard `Transfer-Encoding` should be a comma separated list, with the inner-most encoding first, followed by any further transfer codings, ending with `chunked`.\n\nRequests sent with:\n\n```\nTransfer-Encoding: gzip, chunked\n```\n\nWould incorrectly get ignored, and the request would use a `Content-Length` header instead to determine the body size of the HTTP message.\n\nThis could allow for Waitress to treat a single request as multiple requests in the case of HTTP pipelining.\n\n### Patches\n\nThis issue is fixed in Waitress 1.4.0. This brings a range of changes to harden Waitress against potential HTTP request confusions, and may change the behaviour of Waitress behind non-conformist proxies. \n\nWaitress will now return a 501 Not Implemented error if the `Transfer-Encoding` is not `chunked` or contains multiple elements. Waitress does not support any transfer codings such as `gzip` or `deflate`.\n\nThe Pylons Project recommends upgrading as soon as possible, while validating that the changes in Waitress don\u0026#39;t cause any changes in behavior.\n\n### Workarounds\n\nVarious reverse proxies may have protections against sending potentially bad HTTP requests to the backend, and or hardening against potential issues like this. If the reverse proxy doesn\u0026#39;t use HTTP/1.1 for connecting to the backend issues are also somewhat mitigated, as HTTP pipelining does not exist in HTTP/1.0 and Waitress will close the connection after every single request (unless the Keep Alive header is explicitly sent... so this is not a fool proof security method).\n\n### Issues/more security issues:\n\n* open an issue at https://github.com/Pylons/waitress/issues (if not sensitive or security related)\n* email the Pylons Security mailing list: pylons-project-security@googlegroups.com (if security related)",
  "id": "GHSA-g2xc-35jw-c63p",
  "modified": "2022-04-25T23:07:24Z",
  "published": "2019-12-20T23:04:18Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Pylons/waitress/security/advisories/GHSA-g2xc-35jw-c63p"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2019-16786"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Pylons/waitress/commit/f11093a6b3240fc26830b6111e826128af7771c3"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2020:0720"
    },
    {
      "type": "WEB",
      "url": "https://docs.pylonsproject.org/projects/waitress/en/latest/#security-fixes"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Pylons/waitress"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2022/05/msg00011.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GVDHR2DNKCNQ7YQXISJ45NT4IQDX3LJ7"
    },
    {
      "type": "WEB",
      "url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/LYEOTGWJZVKPRXX2HBNVIYWCX73QYPM5"
    },
    {
      "type": "WEB",
      "url": "https://www.oracle.com/security-alerts/cpuapr2022.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "HTTP Request Smuggling: Invalid Transfer-Encoding in Waitress"
}


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