Resource exhaustion in Agendaless Waitress
CVE-2020-5236
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.
Vulnerability class: DoS (Denial of Service)
EPSS: 0.026 (84.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.7 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H.
Affected products
- Agendaless Waitress — versions 1.4.2
- Pylons Waitress — versions = 1.4.2
Weakness classification (CWE)
Public proof-of-concept exploits
References
- security-advisories@github.com (x_refsource_CONFIRM, Third Party Advisory)
- security-advisories@github.com (Patch, Third Party Advisory, x_refsource_MISC)
Frequently asked questions
- What is CVE-2020-5236?
- CVE-2020-5236 is a medium-severity vulnerability in Agendaless Waitress, classified under Uncontrolled Resource Consumption. CVSS score: 5.7/10. Published 2020-02-04.
- How severe is CVE-2020-5236?
- Medium severity. CVSS v3 base score is 5.7 out of 10.
- Is CVE-2020-5236 known to be exploited?
- 9 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.