James Bennett of the Django Project reports:

Security releases issued

Today the Django team is issuing multiple releases -- Django 1.3.2 and
Django 1.4.1 -- to remedy security issues reported to us.

All users are encouraged to upgrade Django immediately.
 
Denial-of-service in image validation

Django's form system includes field types for handling file uploads,
including a field class -- django.forms.ImageField -- for uploading
images, which can perform some validation of image formats.

Part of that validation involves detecting corrupted image files,
using routines provided by the Python Imaging Library (PIL).

The check as it currently exists in Django is vulnerable, however,
because it will read the entire image file, including decompressing
compressed formats as needed. It is trivially possible to craft a
reasonably-sized file which, when decompressed in this fashion, grows
to enormous size, consuming available memory and offering the ability
to perform a denial-of-service attack.

To mitigate this, image validation will now make use of PIL's
Image.verify() method, which performs some validation checks but does
not decompress or read the entire image file.

References:

https://www.djangoproject.com/weblog/2012/jul/30/security-releases-issued/