HTTP Request Smuggling: Content-Length Sent Twice in Waitress
Impact
Waitress would header fold a double Content-Length header and due to being unable to cast the now comma separated value to an integer would set the Content-Length to 0 internally.
So a request with:
Content-Length: 10
Content-Length: 10would get transformed to:
Content-Length: 10, 10Which would Waitress would then internally set to Content-Lenght: 0.
Waitress would then treat the request as having no body, thereby treating the body of the request as a new request in HTTP pipelining.
Patches
This issue is fixed in Waitress 1.4.0. This brings a range of changes to harden Waitress against potential HTTP request confusions, and may change the behaviour of Waitress behind non-conformist proxies.
The Pylons Project recommends upgrading as soon as possible, while validating that the changes in Waitress don't cause any changes in behavior.
Workarounds
Various reverse proxies may have protections against sending potentially bad HTTP requests to the backend, and or hardening against potential issues like this. If the reverse proxy doesn't use HTTP/1.1 for connecting to the backend issues are also somewhat mitigated, as HTTP pipelining does not exist in HTTP/1.0 and Waitress will close the connection after every single request (unless the Keep Alive header is explicitly sent... so this is not a fool proof security method).
Issues/more security issues:
- open an issue at https://github.com/Pylons/waitress/issues (if not sensitive or security related)
- email the Pylons Security mailing list: pylons-project-security@googlegroups.com (if security related)
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | waitress | < 1.4.0 | 1.4.0 |
References
- https://docs.pylonsproject.org/projects/waitress/en/latest/#security-fixes
- https://github.com/Pylons/waitress/commit/575994cd42e83fd772a5f7ec98b2c56751bd3f65
- https://github.com/Pylons/waitress/security/advisories/GHSA-4ppp-gpcr-7qf6
- https://github.com/advisories/GHSA-j7j6-7hfx-5522
- https://nvd.nist.gov/vuln/detail/CVE-2019-16792
- https://github.com/Pylons/waitress
- https://lists.debian.org/debian-lts-announce/2022/05/msg00011.html
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://github.com/pypa/advisory-database/tree/main/vulns/waitress/PYSEC-2020-178.yaml
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N- Weakness (CWE)
CWE-444- Platform
- Python (PyPI)
- Package
waitress- Disclosed
- 20.12.2019
- Updated
- 11.10.2026 13:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2020-178 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-j7j6-7hfx-5522 - CC BY 4.0
OSV / GitHub Advisory Database - GHSA-4ppp-gpcr-7qf6 - CC BY 4.0
Vulnerability history: waitress
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 10
- First → latest
- 12.2019 10.2024
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 2
- High 4
- Medium 4
Disclosures per year
- 2019: 5
- 2020: 1
- 2021: 0
- 2022: 2
- 2023: 0
- 2024: 2
- 2025: 0
- 2026: 0
-
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