python-django: directory traversal

Rainer Koirikivi discovered a directory traversal vulnerability with 'ssi' template tags in python-django, a high-level Python web development framework.

It was shown that the handling of the 'ALLOWED_INCLUDE_ROOTS' setting, used to represent allowed prefixes for the {% ssi %} template tag, is vulnerable to a directory traversal attack, by specifying a file path which begins as the absolute path of a directory in 'ALLOWED_INCLUDE_ROOTS', and then uses relative paths to break free.

To exploit this vulnerability an attacker must be in a position to alter templates on the site, or the site to be attacked must have one or more templates making use of the 'ssi' tag, and must allow some form of unsanitized user input to be used as an argument to the 'ssi' tag.