[Security] Bump waitress from 1.4.2 to 1.4.3

[dependabot-preview]

Bumps waitress from 1.4.2 to 1.4.3. This update includes a security fix.

Vulnerabilities fixed

Sourced from The GitHub Security Advisory Database.

Critical severity vulnerability that affects waitress

Impact

When waitress receives a header that contains invalid characters it will cause the regular expression engine to catastrophically backtrack causing the process to use 100% CPU time and blocking any other interactions.

This would allow an attacker to send a single request with an invalid header and take the service offline.

Invalid header example:

Bad-header: xxxxxxxxxxxxxxx\x10

Increasing the number of x's in the header will increase the amount of time Waitress spends in the regular expression engine.

This issue was introduced in version 1.4.2 when the regular expression was updated to attempt to match the behaviour required by errata associated with RFC7230.

Patches

The regular expression that is used to validate incoming headers has been updated in version 1.4.3, it is recommended that people upgrade to the new version of Waitress as soon as possible.

... (truncated)

Affected versions: = 1.4.2

Changelog

Sourced from waitress's changelog.

1.4.3 (2020-02-02)

Security Fixes

- In Waitress version 1.4.2 a new regular expression was added to validate the
  headers that Waitress receives to make sure that it matches RFC7230.
  Unfortunately the regular expression was written in a way that with invalid
  input it leads to catastrophic backtracking which allows for a Denial of
  Service and CPU usage going to a 100%.
This was reported by Fil Zembowicz to the Pylons Project. Please see
GHSA-73m2-3pwg-5fgc
for more information.

Commits

• cbc89bf Prep v1.4.3
• 6e46f9e Merge pull request from GHSA-73m2-3pwg-5fgc
• 51b9bd4 Remove accidental backslash
• f87abb7 Add bad header that caused catastrophic backtracking
• 2fe8e54 Add header parsing tests with short headers
• ac0ca05 Remove catastrophic backtracking in regex
• See full diff in compare view

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