QID 983116

QID 983116: Python (pip) Security Update for waitress (GHSA-73m2-3pwg-5fgc)

Security update has been released for waitress to fix the vulnerability.

Note: The preceding description block is extracted directly from the security advisory. Using automation, we have attempted to clean and format it as much as possible without introducing additional issues.

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.

  • CVSS V3 rated as High - 6.5 severity.
  • CVSS V2 rated as High - 6.8 severity.
    • Solution
    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.Workaround:
    If you have deployed a reverse proxy in front of Waitress it may already be rejecting requests that include invalid headers.
    Vendor References

    CVEs related to QID 983116

    CVE-2020-5236 |
    Software Advisories
    Advisory ID Software Component Link
    GHSA-73m2-3pwg-5fgc waitress URL Logo github.com/advisories/GHSA-73m2-3pwg-5fgc
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