CVE-2019-16785: HTTP Request Smuggling: LF vs CRLF handling in Waitress

CVE-2019-16785 · Severity: low · CVSS 3.1 · Published 2019-12-20

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.

Technologies: waitress (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2019-16785 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2019-16785 being exploited in the wild.
How severe is CVE-2019-16785?
Low severity, with a CVSS score of 3.1, published 20 December 2019.
Which products and versions are affected?
waitress (PyPI) ECOSYSTEM:introduced=0,fixed=1.4.0, GIT:introduced=0,fixed=8eba394ad75deaf9e5cd15b78a3d16b12e6b0eba|ECOSYSTEM:introduced=0,fixed=1.4.0.
Is there a fix for CVE-2019-16785?
Yes. waitress (PyPI): upgrade to 1.4.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2019-16785?
Check whether you run waitress (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • waitress (PyPI): upgrade to 1.4.0 or later
    pip install "waitress>=1.4.0"

Affected products

  • waitress (PyPI) ECOSYSTEM:introduced=0,fixed=1.4.0, GIT:introduced=0,fixed=8eba394ad75deaf9e5cd15b78a3d16b12e6b0eba|ECOSYSTEM:introduced=0,fixed=1.4.0

Identifiers

  • CVE-2019-16785
  • GHSA-pg36-wpm5-g57p
  • PYSEC-2019-136

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