Django 4.2.6 release notes

October 4, 2023

Django 4.2.6 fixes a security issue with severity “moderate” and several bugs in 4.2.5.

CVE-2023-43665: Denial-of-service possibility in django.utils.text.Truncator

Following the fix for CVE-2019-14232, the regular expressions used in the implementation of django.utils.text.Truncator’s chars() and words() methods (with html=True) were revised and improved. However, these regular expressions still exhibited linear backtracking complexity, so when given a very long, potentially malformed HTML input, the evaluation would still be slow, leading to a potential denial of service vulnerability.

The chars() and words() methods are used to implement the truncatechars_html and truncatewords_html template filters, which were thus also vulnerable.

The input processed by Truncator, when operating in HTML mode, has been limited to the first five million characters in order to avoid potential performance and memory issues.

Bugfixes

  • Fixed a regression in Django 4.2.5 where overriding the deprecated DEFAULT_FILE_STORAGE and STATICFILES_STORAGE settings in tests caused the main STORAGES to mutate (#34821).

  • Fixed a regression in Django 4.2 that caused unnecessary casting of string based fields (CharField, EmailField, TextField, CICharField, CIEmailField, and CITextField) used with the __isnull lookup on PostgreSQL. As a consequence, the pre-Django 4.2 indexes didn’t match and were not used by the query planner (#34840).

    You may need to recreate indexes propagated to the database with Django 4.2 - 4.2.5 as they contain unnecessary ::text casting that is avoided as of this release.