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.

How to fix CVE-2020-5236

To remediate CVE-2020-5236, upgrade the affected package to a fixed version below.

• —upgrade to 1.4.3 or later
• —upgrade to 6e46f9e3f014d64dd7d1e258eaf626e39870ee1f or later

Is CVE-2020-5236 being exploited?

Moderate — EPSS is 13.3%. Track this CVE but it's not at the top of the prioritisation list.

Affected packages (2)

• >= 1.4.2, < 1.4.3
• from 0, < 6e46f9e3f014d64dd7d1e258eaf626e39870ee1f | from 0, < 1.4.3

CVSS scores

References (5)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2020-5236
• PATCHgithub.com/Pylons/waitress
• WEBgithub.com/Pylons/waitress/commit/6e46f9e3f014d64dd7d1e258eaf626e39870ee1f
• WEBgithub.com/Pylons/waitress/security/advisories/GHSA-73m2-3pwg-5fgc