Vulnerability CVE-2020-5236


Published: 2020-02-04

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.

Type:

CWE-400

(Uncontrolled Resource Consumption ('Resource Exhaustion'))

CVSS2 => (AV:N/AC:L/Au:S/C:N/I:N/A:C)

CVSS Base Score
Impact Subscore
Exploitability Subscore
6.8/10
6.9/10
8/10
Exploit range
Attack complexity
Authentication
Remote
Low
Single time
Confidentiality impact
Integrity impact
Availability impact
None
None
Complete
Affected software
Agendaless -> Waitress 

 References:
https://github.com/Pylons/waitress/commit/6e46f9e3f014d64dd7d1e258eaf626e39870ee1f
https://github.com/Pylons/waitress/security/advisories/GHSA-73m2-3pwg-5fgc

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