Django: CVE-2021-32052: Header injection possibility since URLValidator accepted newlines in input on Python 3.9.5+

[Mariusz Felisiak <felisiak.mariusz () gmail com>]

https://www.djangoproject.com/weblog/2021/may/06/security-releases/

In accordance with `our security release policy
<https://docs.djangoproject.com/en/dev/internals/security/>`_, the 
Django team
is issuing
`Django 3.2.2 <https://docs.djangoproject.com/en/dev/releases/3.2.2/>`_,
`Django 3.1.10 
<https://docs.djangoproject.com/en/dev/releases/3.1.10/>`_, and
`Django 2.2.22 <https://docs.djangoproject.com/en/dev/releases/2.2.22/>`_.
These releases address the security issue with severity "moderate" 
detailed below. We encourage all users of Django to upgrade as soon as 
possible.

CVE-2021-32052: Header injection possibility since ``URLValidator`` 
accepted newlines in input on Python 3.9.5+
===============================================================================================================

On Python 3.9.5+, ``URLValidator`` didn't prohibit
newlines and tabs. If you used values with newlines in HTTP response, 
you could
suffer from header injection attacks. Django itself wasn't vulnerable 
because
``HttpResponse`` prohibits newlines in HTTP headers.

Moreover, the ``URLField`` form field which uses ``URLValidator`` silently
removes newlines and tabs on Python 3.9.5+, so the possibility of newlines
entering your data only existed if you are using this validator outside 
of the
form fields.

This issue was introduced by the `bpo-43882 
<https://bugs.python.org/issue43882>`_ fix.

Affected supported versions
===========================

* Django main branch
* Django 3.2
* Django 3.1
* Django 2.2

Resolution
==========

Patches to resolve the issue have been applied to Django's main branch 
and to
the 3.2, 3.1, and 2.2 release branches. The patches may be obtained from the
following changesets:

* On the `main branch 
<https://github.com/django/django/commit/e1e81aa1c4427411e3c68facdd761229ffea6f6f>`__
* On the `3.2 release branch 
<https://github.com/django/django/commit/2d2c1d0c97832860fbd6597977e2aae17dd7e5b2>`__
* On the `3.1 release branch 
<https://github.com/django/django/commit/afb23f5929944a407e4990edef1c7806a94c9879>`__
* On the `2.2 release branch 
<https://github.com/django/django/commit/d9594c4ea57b6309d93879805302cec9ae9f23ff>`__

The following releases have been issued:

* Django 3.2.2 (`download Django 3.2.2 
<https://www.djangoproject.com/m/releases/3.2/Django-3.2.2.tar.gz>`_ | 
`3.2.2 checksums 
<https://www.djangoproject.com/m/pgp/Django-3.2.2.checksum.txt>`_)
* Django 3.1.10 (`download Django 3.1.10 
<https://www.djangoproject.com/m/releases/3.1/Django-3.1.10.tar.gz>`_ | 
`3.1.10 checksums 
<https://www.djangoproject.com/m/pgp/Django-3.1.10.checksum.txt>`_)
* Django 2.2.22 (`download Django 2.2.22 
<https://www.djangoproject.com/m/releases/2.2/Django-2.2.22.tar.gz>`_ | 
`2.2.22 checksums 
<https://www.djangoproject.com/m/pgp/Django-2.2.22.checksum.txt>`_)

The PGP key ID used for this release is Mariusz Felisiak: 
`2EF56372BA48CD1B <https://github.com/felixxm.gpg>`_.

General notes regarding security reporting
==========================================

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