potential denial of service attack via the locale parameter

How it was found

In Django 3.2 before 3.2.16, 4.0 before 4.0.8, and 4.1 before 4.1.2, internationalized URLs were subject to a denial of service attack via the locale parameter, which is treated as a regular expression.

Impact

By crafting a Python regex, a vulnerable site could suffer a DOS attack. The attack was most likely to happen on sites that processes locale IDs from URL parameters.