SB2019122103 - Inconsistent interpretation of HTTP requests in waitress

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Main Vulnerability Database SB2019122103

SB2019122103 - Inconsistent interpretation of HTTP requests in waitress

Published: December 21, 2019 Updated: August 3, 2020

Security Bulletin ID SB2019122103
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-2019-16785)

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

Waitress through version 1.3.1 implemented a "MAY" part of the RFC7230 which states: "Although the line terminator for the start-line and header fields is the sequence CRLF, a recipient MAY recognize a single LF as a line terminator and ignore any preceding CR." Unfortunately if a front-end server does not parse header fields with an LF the same way as it does those with a CRLF it can lead to the front-end and the back-end server parsing the same HTTP message in two different ways. This can lead to a potential for HTTP request smuggling/splitting whereby Waitress may see two requests while the front-end server only sees a single HTTP message. This issue is fixed in Waitress 1.4.0.


Remediation

Install update from vendor's website.

References