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Date: Wed, 1 Nov 2023 08:04:37 +0100
From: Mariusz Felisiak <>
Subject: Django: CVE-2023-46695: Potential denial of service vulnerability in
 UsernameField on Windows

In accordance with `our security release policy
<>`_, the 
Django team
is issuing
`Django 4.2.7 <>`_,
`Django 4.1.13 
<>`_, and
`Django 3.2.23 <>`_.
These releases addresses the security issue detailed below. We encourage all
users of Django to upgrade as soon as possible.

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 
of service attack via certain inputs with a very large number of Unicode

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

Thanks `MProgrammer <>`_ for the report.

This issue has severity "moderate" according to the Django security policy.

Affected supported versions

* Django main branch
* Django 5.0 (currently at beta status)
* Django 4.2
* Django 4.1
* Django 3.2


Patches to resolve the issue have been applied to Django's main branch 
and the
5.0, 4.2, 4.1, and 3.2 release branches. The patches may be obtained 
from the
following changesets:

* On the `main branch 
* On the `5.0 release branch 
* On the `4.2 release branch 
* On the `4.1 release branch 
* On the `3.2 release branch 

The following releases have been issued:

* Django 4.2.7 (`download Django 4.2.7 
<>`_ | 
`4.2.7 checksums 
* Django 4.1.13 (`download Django 4.1.13 
<>`_ | 
`4.1.13 checksums 
* Django 3.2.23 (`download Django 3.2.23 
<>`_ | 
`3.2.23 checksums 

The PGP key ID used for this release is Mariusz Felisiak: 
`2EF56372BA48CD1B <>`_.

General notes regarding security reporting

As always, we ask that potential security issues be reported via
private email to ````, and not via Django's
Trac instance or the django-developers list. Please see `our security
policies <>`_ for further

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