# Django 5.2.17 documentation

# Django 4.2.7 release notes

November 1, 2023

Django 4.2.7 fixes a security issue with severity “moderate” and several bugs in 4.2.6.

## CVE-2023-46695: Potential denial of service vulnerability in `UsernameField` on Windows

The `NFKC normalization` is slow on Windows. As a consequence, `django.contrib.auth.forms.UsernameField` was subject to a potential denial of service attack via certain inputs with a very large number of Unicode characters.

In order to avoid the vulnerability, invalid values longer than `UsernameField.max_length` are no longer normalized, since they cannot pass validation anyway.

## Bugfixes

- Fixed a regression in Django 4.2 that caused a crash of `QuerySet.aggregate()` with aggregates referencing expressions containing subqueries (#34798).

- Restored, following a regression in Django 4.2, creating `varchar/text_pattern_ops` indexes on `CharField` and `TextField` with deterministic collations on PostgreSQL (#34932).