Mastering Django: Core

Session serialization

Before version 1.6, Django defaulted to using pickle to serialize session data before storing it in the backend. If you're using the signed cookie session backend and SECRET_KEY is known by an attacker (there isn't an inherent vulnerability in Django that would cause it to leak), the attacker could insert a string into their session which, when unpickled, executes arbitrary code on the server. The technique for doing so is simple and easily available on the internet.

Although the cookie session storage signs the cookie-stored data to prevent tampering, a SECRET_KEY leak immediately escalates to a remote code execution vulnerability. This attack can be mitigated by serializing session data using JSON rather than pickle. To ...