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.
https://www.oracle.com/security-alerts/cpuapr2022.html
https://lists.debian.org/debian-lts-announce/2022/05/msg00011.html
https://github.com/Pylons/waitress/security/advisories/GHSA-pg36-wpm5-g57p
https://github.com/Pylons/waitress/commit/8eba394ad75deaf9e5cd15b78a3d16b12e6b0eba
https://docs.pylonsproject.org/projects/waitress/en/latest/#security-fixes
Published: 2019-12-20
Updated: 2023-11-07
Base Score: 5
Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:P/A:N
Severity: Medium
Base Score: 7.5
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Severity: High
Base Score: 5.1
Vector: 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
Severity: Medium