CVE-2019-16786: HTTP Request Smuggling Invalid Transfer-Encoding Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-g2xc-35jw-c63p",
  "modified" : "2024-11-19T13:57:29Z",
  "published" : "2019-12-20T23:04:18Z",
  "aliases" : [ "CVE-2019-16786" ],
  "summary" : "HTTP Request Smuggling: Invalid Transfer-Encoding in Waitress",
  "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'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'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)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "waitress"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.4.0"
      } ]
    } ]
  } ],
  "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://github.com/pypa/advisory-database/tree/main/vulns/waitress/PYSEC-2019-137.yaml"
  }, {
    "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-444" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2019-12-20T23:01:53Z",
    "nvd_published_at" : "2019-12-20T23:15:00Z"
  }
}