{"id":"CVE-2019-16786","aliases":["GHSA-g2xc-35jw-c63p","PYSEC-2019-137"],"url":"https://o3.security/vulnerability/CVE-2019-16786","summary":"HTTP Request Smuggling: Invalid Transfer-Encoding in Waitress","details":"Waitress through version 1.3.1 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. This issue is fixed in Waitress 1.4.0.","published":"2019-12-20T23:15:11.277Z","modified":"2026-07-08T05:59:33.459442532Z","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/f11093a6b3240fc26830b6111e826128af7771c3","label":"Pylons/waitress@f11093a"},"references":[{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GVDHR2DNKCNQ7YQXISJ45NT4IQDX3LJ7/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LYEOTGWJZVKPRXX2HBNVIYWCX73QYPM5/"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2020:0720"},{"type":"ADVISORY","url":"https://docs.pylonsproject.org/projects/waitress/en/latest/#security-fixes"},{"type":"ADVISORY","url":"https://github.com/Pylons/waitress/security/advisories/GHSA-g2xc-35jw-c63p"},{"type":"ADVISORY","url":"https://lists.debian.org/debian-lts-announce/2022/05/msg00011.html"},{"type":"FIX","url":"https://github.com/Pylons/waitress/commit/f11093a6b3240fc26830b6111e826128af7771c3"},{"type":"FIX","url":"https://www.oracle.com/security-alerts/cpuapr2022.html"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-08T05:59:33.459442532Z"}}