CVE-2020-5236

Name	CVE-2020-5236
Description	Waitress version 1.4.2 allows a DOS attack When waitress receives a header that contains invalid characters. When a header like "Bad-header: xxxxxxxxxxxxxxx\x10" is received, it will cause the regular expression engine to catastrophically backtrack causing the process to use 100% CPU time and blocking any other interactions. This allows an attacker to send a single request with an invalid header and take the service offline. This issue was introduced in version 1.4.2 when the regular expression was updated to attempt to match the behaviour required by errata associated with RFC7230. The regular expression that is used to validate incoming headers has been updated in version 1.4.3, it is recommended that people upgrade to the new version of Waitress as soon as possible.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
waitress (PTS)	jessie, jessie (lts)	0.8.9-2+deb8u1	fixed
	stretch (security), stretch (lts), stretch	1.0.1-1+deb9u1	fixed
	buster (security), buster, buster (lts)	1.2.0~b2-2+deb10u1	fixed
	bullseye (security), bullseye	1.4.4-1.1+deb11u1	fixed
	bookworm	2.1.2-2	fixed
	sid, trixie	3.0.1-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
waitress	source	wheezy	(unfixed)	end-of-life
waitress	source	(unstable)	(not affected)

Notes

- waitress <not-affected> (Vulnerable code introduced later)
https://github.com/Pylons/waitress/security/advisories/GHSA-73m2-3pwg-5fgc
Introduced in: https://github.com/Pylons/waitress/commit/0bf98dadd8cae23830cb365cc6cb9cedd7f98db0 (v1.4.2)
https://github.com/Pylons/waitress/commit/6e46f9e3f014d64dd7d1e258eaf626e39870ee1f (v1.4.3)