CVE catalog
CVE-2020-5236
waitress: CVE-2020-5236
- Severity
- Medium · CVSS 6.5
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 2.36% · Oct 25, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | waitress | sid | 3.0.2-2 | not affected |
| Debian | waitress | forky | 3.0.2-2 | not affected |
| Debian | waitress | trixie | 3.0.2-1 | not affected |
| Debian | waitress | bookworm | 2.1.2-2+deb12u1 | not affected |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | waitress | source | sid | Not affected | unimportant | Not reported | Not reported |
| Debian | waitress | source | forky | Not affected | unimportant | Not reported | Not reported |
| Debian | waitress | source | trixie | Not affected | unimportant | Not reported | Not reported |
| Debian | waitress | source | bookworm | Not affected | unimportant | Not reported | Not reported |
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [python3-waitress]Not affected
Source package: [waitress]
Details (2)
2.1.2-2+deb12u1· all · bookwormNot affected
dsa · waitress · debian · bookworm
2.1.2-2+deb12u1· all · bookwormNot affected
dsa · waitress · debian · bookworm
- [python-waitress-doc]Not affected
Source package: [waitress]
Details (2)
2.1.2-2+deb12u1· all · bookwormNot affected
dsa · waitress · debian · bookworm
2.1.2-2+deb12u1· all · bookwormNot affected
dsa · waitress · debian · bookworm
Observed: