A flask-security security update has been released for Debian GNU/Linux 10 LTS to address an issue where it is possible to bypass URL validation and redirect a user to an arbitrary URL by providing multiple back slashes such as \\\evil.com/path.

[SECURITY] [DLA 3545-1] flask-security security update

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Debian LTS Advisory DLA-3545-1 debian-lts@lists.debian.org
https://www.debian.org/lts/security/ Sean Whitton
August 28, 2023 https://wiki.debian.org/LTS
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Package : flask-security
Version : 1.7.5-2+deb10u1
CVE ID : CVE-2021-23385
Debian Bug : 1021279

It was discovered that when using the get_post_logout_redirect and
get_post_login_redirect functions in flask-security, an implementation
of simple security for Flask apps, it is possible to bypass URL
validation and redirect a user to an arbitrary URL by providing multiple
back slashes such as \\\evil.com/path.

This vulnerability is exploitable only if an alternative WSGI server
other than Werkzeug is used, or the default behaviour of Werkzeug is
modified using 'autocorrect_location_header=False.

For Debian 10 buster, this problem has been fixed in version
1.7.5-2+deb10u1.

We recommend that you upgrade your flask-security packages.

For the detailed security status of flask-security please refer to
its security tracker page at:
https://security-tracker.debian.org/tracker/flask-security

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://wiki.debian.org/LTS