Home/CVE/Waitress version 1.4.2 allows a DOS attack When waitress receives a header that contains invalid characters. When a head
CVE

CVE-2020-5236

Waitress version 1.4.2 allows a DOS attack When waitress receives a header that contains invalid characters. When a head

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.

MEDIUM · CVSS 5.7 EPSS 0.13332
Schedule remediation
  • EPSS ≥ 0.10 - elevated exploitation probability
  • EPSS percentile: top 6% of all CVEs by exploitation likelihood
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-400Uncontrolled Resource Consumption
CWE-400Uncontrolled Resource Consumption
▤

Affected Products & Versions

1
agendaless waitressall versions
▤

Affected Packages

1
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
PyPI waitress MODERATE fixed in 1.4.3
▣

Scoring & Timeline

5.7
MEDIUM · CVSS v3.1 · security-advisories@github.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD04 Feb 2020 · 03:15 AM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
🔗

References & Sources

2
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/Pylons/waitress/commit/6e46f9e3f014d64dd7d1e258eaf626e39870ee1fPatchThird Party Advisory
https://github.com/Pylons/waitress/security/advisories/GHSA-73m2-3pwg-5fgcThird Party Advisory
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