{"id":"CVE-2019-16785","aliases":["GHSA-pg36-wpm5-g57p","PYSEC-2019-136"],"url":"https://o3.security/vulnerability/CVE-2019-16785","summary":"HTTP Request Smuggling: LF vs CRLF handling in Waitress","details":"Waitress through version 1.3.1 implemented a \"MAY\" part of the RFC7230 which states: \"Although the line terminator for the start-line and header fields is the sequence CRLF, a recipient MAY recognize a single LF as a line terminator and ignore any preceding CR.\" Unfortunately if a front-end server does not parse header fields with an LF the same way as it does those with a CRLF it can lead to the front-end and the back-end server parsing the same HTTP message in two different ways. This can lead to a potential for HTTP request smuggling/splitting whereby Waitress may see two requests while the front-end server only sees a single HTTP message. This issue is fixed in Waitress 1.4.0.","published":"2019-12-20T23:15:11.167Z","modified":"2026-07-08T05:59:27.954121057Z","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":null,"affectedPackages":[{"ecosystem":"PyPI","name":"waitress","fixedVersion":"1.4.0"}],"fix":{"url":"https://github.com/Pylons/waitress/commit/8eba394ad75deaf9e5cd15b78a3d16b12e6b0eba","label":"Pylons/waitress@8eba394"},"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://lists.debian.org/debian-lts-announce/2022/05/msg00011.html"},{"type":"FIX","url":"https://github.com/Pylons/waitress/commit/8eba394ad75deaf9e5cd15b78a3d16b12e6b0eba"},{"type":"FIX","url":"https://www.oracle.com/security-alerts/cpuapr2022.html"},{"type":"EVIDENCE","url":"https://github.com/Pylons/waitress/security/advisories/GHSA-pg36-wpm5-g57p"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-08T05:59:27.954121057Z"}}