SB2020031156 - Inconsistent interpretation of HTTP requests in py3-waitress (Alpine package)

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

• https://git.alpinelinux.org/aports/commit/?id=bdf9e7d1c8dd8658479cd5d2032b3fbc682d2620
• https://git.alpinelinux.org/aports/commit/?id=27d1b5c609ffa40740bceb1a93245bb57d8b2c2d