[3.7] bpo-39503: CVE-2020-8492: Fix AbstractBasicAuthHandler (GH-18284) by miss-islington · Pull Request #19292 · python/cpython

the-knights-who-say-ni

The AbstractBasicAuthHandler class of the urllib.request module uses
an inefficient regular expression which can be exploited by an
attacker to cause a denial of service. Fix the regex to prevent the
catastrophic backtracking. Vulnerability reported by Ben Caller
and Matt Schwager.

AbstractBasicAuthHandler of urllib.request now parses all
WWW-Authenticate HTTP headers and accepts multiple challenges per
header: use the realm of the first Basic challenge.

Co-Authored-By: Serhiy Storchaka <storchaka@gmail.com>
(cherry picked from commit 0b297d4)

Co-authored-by: Victor Stinner <vstinner@python.org>