CVE-2019-16789HTTP Request Smuggling in Waitress: Invalid whitespace characters in headers
- 7.1HighCVSS base score
- 2.6%Exploitation in 30 daysEPSS · top 14% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In Waitress through version 1.4.0, if a proxy server is used in front of waitress, an invalid request may be sent by an attacker that bypasses the front-end and is parsed differently by waitress leading to a potential for HTTP request smuggling. Specially crafted requests containing special whitespace characters in the Transfer-Encoding header would get parsed by Waitress as being a chunked request, but a front-end server would use the Content-Length instead as the Transfer-Encoding header is considered invalid due to containing invalid characters. If a front-end server does HTTP pipelining to a backend Waitress server this could lead to HTTP request splitting which may lead to potential cache poisoning or unexpected information disclosure. This issue is fixed in Waitress 1.4.1 through more strict HTTP field validation.
Timeline
ID reserved
By GitHub_M
- 3 months later
· 3 months later
Published
- 5 years later
· 5 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High7.1 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:H/A:N |
| NVDNVD · Modified | 3.1 | High8.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N |
- EPSS (exploitation in 30 days)
- 2.6% · top 14% of all CVEs (13 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.1.
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- PyPIwaitressGHSA-968f-66r5-5v74 (opens in a new tab)
What to do
Workaround: You may enable additional protections on front-end servers, those that follow RFC7230 correctly would drop the request with a 400 Bad Request. Waitress will now correctly responds to the request with a 400 Bad Request, and will drop the connection to avoid any potential HTTP pipelining issues.
References
References8
- FEDORA-2020-bdcc8ffc24 (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- FEDORA-2020-65a7744e38 (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- RHSA-2020:0720 (opens in a new tab)vendor-advisoryx_refsource_REDHATx_transferred
- https://www.oracle.com/security-alerts/cpuapr2022.html (opens in a new tab)x_refsource_MISCx_transferred
- https://docs.pylonsproject.org/projects/waitress/en/latest/#security-fixes (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/github/advisory-review/pull/14604 (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://github.com/Pylons/waitress/commit/11d9e138125ad46e951027184b13242a3c1de017 (opens in a new tab)x_refsource_MISCx_transferred
- [debian-lts-announce] 20220512 [SECURITY] [DLA 3000-1] waitress security update (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2019-0158 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-968f-66r5-5v74 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2019-16789)Record last updated .