SB2019122102 - Inconsistent interpretation of HTTP requests in waitress

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Main Vulnerability Database SB2019122102

SB2019122102 - Inconsistent interpretation of HTTP requests in waitress

Published: December 21, 2019 Updated: July 17, 2020

Security Bulletin ID SB2019122102
Severity
Medium
Patch available
YES
Number of vulnerabilities 1
Exploitation vector Remote access
Highest impact Data manipulation

Breakdown by Severity

Medium 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 1 security vulnerability.


1) Inconsistent interpretation of HTTP requests (CVE-ID: CVE-2019-16786)

The vulnerability allows a remote non-authenticated attacker to manipulate data.

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.


Remediation

Install update from vendor's website.

References