CVE-2018-20852

http.cookiejar.DefaultPolicy.domain_return_ok in Lib/http/cookiejar.py in
Python before 3.7.3 does not correctly validate the domain: it can be
tricked into sending existing cookies to the wrong server. An attacker may
abuse this flaw by using a server with a hostname that has another valid
hostname as a suffix (e.g., pythonicexample.com to steal cookies for
example.com). When a program uses http.cookiejar.DefaultPolicy and tries to
do an HTTP connection to an attacker-controlled server, existing cookies
can be leaked to the attacker. This affects 2.x through 2.7.16, 3.x before
3.4.10, 3.5.x before 3.5.7, 3.6.x before 3.6.9, and 3.7.x before 3.7.3.

Bugs

• <https://bugs.python.org/issue35121&gt;