Waitress
CVE-2019-16786
HIGH
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V4 - API and Web Service HTTP request consistency
|
| Impact | CVSS score of 7.5 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. |
| Exploit ScenarioDerived | A remote attacker could manipulate HTTP request interpretation between frontend and backend servers by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability. |
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Alert meAnalysisAI
Waitress through version 1.3.1 would parse the Transfer-Encoding header and only look for a single string value, if that value was not chunked it would fall through and use the Content-Length header. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This HTTP Request/Response Smuggling vulnerability could allow attackers to manipulate HTTP request interpretation between frontend and backend servers.
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Enforce strict HTTP parsing, normalize requests at proxy layer, use HTTP/2 end-to-end, reject ambiguous headers.
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in pypi
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Technical ContextAI · show details
This vulnerability is classified as HTTP Request/Response Smuggling (CWE-444), which allows attackers to manipulate HTTP request interpretation between frontend and backend servers. Waitress through version 1.3.1 would parse the Transfer-Encoding header and only look for a single string value, if that value was not chunked it would fall through and use the Content-Length header instead. According to the HTTP standard Transfer-Encoding should be a comma separated list, with the inner-most encoding first, followed by any further transfer codings, ending with chunked. Requests sent with: "Transfer-Encoding: gzip, chunked" would incorrectly get ignored, and the request would use a Content-Length header instead to determine the body size of the HTTP message. This could allow for Waitress to treat a single request as multiple requests in the case of HTTP pipelining. This issue is fixed in Waitress 1.4.0. Affected products include: Agendaless Waitress, Oracle Communications Cloud Native Core Network Function Cloud Native Environment, Debian Debian Linux, Fedoraproject Fedora, Redhat Openstack. Version information: version 1.3.1.
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Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionNVD
Waitress through version 1.3.1 would parse the Transfer-Encoding header and only look for a single string value, if that value was not chunked it would fall through and use the Content-Length header instead. According to the HTTP standard Transfer-Encoding should be a comma separated list, with the inner-most encoding first, followed by any further transfer codings, ending with chunked. Requests sent with: "Transfer-Encoding: gzip, chunked" would incorrectly get ignored, and the request would use a Content-Length header instead to determine the body size of the HTTP message. This could allow for Waitress to treat a single request as multiple requests in the case of HTTP pipelining. This issue is fixed in Waitress 1.4.0.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
HTTP request smuggling exploits inconsistencies in how front-end and back-end servers parse HTTP message boundaries.
Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.
Affected Products (CPE)NVD
Waitress through version 1.3.1 implemented a "MAY" part of the RFC7230 which states: "Although the line terminator for t
Waitress is a Web Server Gateway Interface server for Python 2 and 3. Rated medium severity (CVSS 5.9), this vulnerabili
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
Waitress is a Web Server Gateway Interface server for Python 2 and 3. Rated high severity (CVSS 7.5), this vulnerability
Waitress is a Web Server Gateway Interface server for Python 2 and 3. Rated high severity (CVSS 7.5), this vulnerability
Waitress version 1.4.2 allows a DOS attack When waitress receives a header that contains invalid characters. Rated mediu
Waitress is a Web Server Gateway Interface server for Python 2 and 3. Rated medium severity (CVSS 4.8), this vulnerabili
Exploit-DB