SB2020031155 - 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-2019-16785)

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

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