{"id":"CVE-2019-16792","aliases":["GHSA-4ppp-gpcr-7qf6","GHSA-j7j6-7hfx-5522","PYSEC-2020-178"],"url":"https://o3.security/vulnerability/CVE-2019-16792","summary":"HTTP Request Smuggling: Content-Length Sent Twice in Waitress","details":"### Impact\n\nWaitress would header fold a double `Content-Length` header and due to being unable to cast the now comma separated value to an integer would set the `Content-Length` to 0 internally.\n\nSo a request with:\n\n```\nContent-Length: 10\nContent-Length: 10\n```\n\nwould get transformed to:\n\n```\nContent-Length: 10, 10\n```\n\nWhich would Waitress would then internally set to `Content-Lenght: 0`.\n\nWaitress would then treat the request as having no body, thereby treating the body of the request as a new request in 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\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)","published":"2020-01-22T19:15:11.140Z","modified":"2026-07-08T05:59:33.147473606Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"waitress","fixedVersion":"1.4.0"}],"fix":{"url":"https://github.com/Pylons/waitress/commit/575994cd42e83fd772a5f7ec98b2c56751bd3f65","label":"Pylons/waitress@575994c"},"references":[{"type":"ADVISORY","url":"https://docs.pylonsproject.org/projects/waitress/en/latest/#security-fixes"},{"type":"ADVISORY","url":"https://github.com/Pylons/waitress/security/advisories/GHSA-4ppp-gpcr-7qf6"},{"type":"ADVISORY","url":"https://lists.debian.org/debian-lts-announce/2022/05/msg00011.html"},{"type":"FIX","url":"https://github.com/Pylons/waitress/commit/575994cd42e83fd772a5f7ec98b2c56751bd3f65"},{"type":"FIX","url":"https://www.oracle.com/security-alerts/cpuapr2022.html"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2019-16792"},{"type":"PACKAGE","url":"https://github.com/Pylons/waitress"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/waitress/PYSEC-2020-178.yaml"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-08T05:59:33.147473606Z"}}