CVE-2019-16786

What it is

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.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of data exposure.

Exploit odds

2.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2019-12-20 23:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 02:22 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 2.4% in the next 30 days (EPSS).
• Severity: 7.1 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2019-12-20 23:15 UTC

Last modified

2026-06-17 02:22 UTC

Exploit probability

2.4% · EPSS, next 30 days

Weakness

CWE-444

Record status

Modified

Affected

• Agendaless Waitress < 1.3.1
• Oracle Communications Cloud Native Core Network Function Cloud Native Environment 1.10.0
• Debian Linux 9.0
• Fedoraproject Fedora 30
• Fedoraproject Fedora 31
• Redhat Openstack 15

Attack profile CVSS 3.1 · 7.1

Attack vector

Network

Complexity

High

Privileges needed

Low

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

Low

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2019-16786.md and follow it. Check whether this project is affected by CVE-2019-16786. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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