{"schema_version":"1.9.0","id":"GHSA-4ppp-gpcr-7qf6","published":"2019-12-20T23:04:35Z","modified":"2026-07-08T06:00:30.894868366Z","aliases":["CVE-2019-16792","GHSA-j7j6-7hfx-5522","PYSEC-2020-178"],"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)","affected":[{"package":{"name":"waitress","ecosystem":"PyPI","purl":"pkg:pypi/waitress"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.4.0"}]}],"versions":["0.1","0.2","0.3","0.4","0.5","0.6","0.6.1","0.7","0.8","0.8.1","0.8.10","0.8.11b0","0.8.2","0.8.3","0.8.4","0.8.5","0.8.6","0.8.7","0.8.8","0.8.9","0.9.0","0.9.0b0","0.9.0b1","1.0.0","1.0.1","1.0.2","1.0a1","1.0a2","1.1.0","1.2.0","1.2.0b1","1.2.0b2","1.2.0b3","1.2.1","1.3.0","1.3.0b0","1.3.1"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2019/12/GHSA-4ppp-gpcr-7qf6/GHSA-4ppp-gpcr-7qf6.json"}}],"references":[{"type":"WEB","url":"https://github.com/Pylons/waitress/security/advisories/GHSA-4ppp-gpcr-7qf6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2019-16792"},{"type":"WEB","url":"https://github.com/Pylons/waitress/commit/575994cd42e83fd772a5f7ec98b2c56751bd3f65"},{"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-2020-178.yaml"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2022/05/msg00011.html"},{"type":"WEB","url":"https://www.oracle.com/security-alerts/cpuapr2022.html"}],"database_specific":{"cwe_ids":["CWE-444"],"github_reviewed":true,"github_reviewed_at":"2019-12-20T23:02:03Z","nvd_published_at":null,"severity":"CRITICAL"}}