=======================================================================
title: Arbitrary File Upload and Bypassing .htaccess Rules
product: Monospace Directus Headless CMS
vulnerable version: < v8.8.2
fixed version: v8.8.2, v9 is not affected because of different architecture
CVE number: CVE-2021-29641
impact: High
homepage: https://directus.io/
found: 2020-12-15
by: Oliver Boehlk (Atos Germany)
Moritz Friedmann (Atos Germany)
SEC Consult Vulnerability Lab
An integrated part of SEC Consult, an Atos company
Europe | Asia | North America
https://www.sec-consult.com
=======================================================================
Vendor description:
-------------------
"Directus Open-Source, Free & Unlimited. No Strings Attached.
Our premium software is available at no cost for commercial and
personal use.
This self-hosted version is full-featured, with no artificial
limitations."
Source: https://directus.io/open-source/
Business recommendation:
------------------------
The vendor provides an updated version for v8 which fixes the
security issue. It should
be installed immediately.
Note: Directus v8 has been deprecated/discontinued and is
replaced by version 9,
which currently does not have a final release version yet. Updating
to Directus v9
fixes this vulnerability as well because the NodeJS architecture
replaces
the PHP API
and hence is not affected.
According to the vendor, the identified security issue only
applies to v8
installations
relying on the specific Apache-based config in the Docker image,
using the local-storage
driver for uploads. The recommendation from the vendor is to use a
connection to S3 for
such installations, install the patch v8.8.2 or upgrade to version
9.
Vulnerability overview/description:
-----------------------------------
1) Arbitrary File Upload and Bypassing .htaccess Rules
(CVE-2021-29641)
Any low privileged user with file upload permissions can upload
webshells
or
other malicious PHP files which can be found in
/uploads/_/originals/.
If the server prevents the execution of PHP files in the upload
directory
the
attacker can move the file into a subdirectory where he can upload
a custom .htaccess
file to enable PHP execution again.
Server side command execution can be used to retrieve the
Directus configuration
and database credentials to escalate in-app privileges, retrieve
password
hashes
or move laterally in the network.
Proof of concept:
-----------------
1) Arbitrary File Upload and Bypassing .htaccess Rules
(CVE-2021-29641)
A PoC environment can be created using a docker-compose.yml
file:
version: "3"
services:
app:
image: directus/directus:v8.8.1-apache
ports:
- 8080:80
environment:
DIRECTUS_INSTALL_TITLE: vulnerable directus server
DIRECTUS_INSTALL_EMAIL:
DIRECTUS_INSTALL_PASSWORD: admin1
DIRECTUS_AUTH_SECRETKEY: directusprivtest
DIRECTUS_AUTH_PUBLICKEY: directuspubtest
DIRECTUS_DATABASE_HOST: db
DIRECTUS_DATABASE_NAME: directus
DIRECTUS_DATABASE_USERNAME: directus
DIRECTUS_DATABASE_PASSWORD: directus
db:
image: mariadb
environment:
MYSQL_ROOT_PASSWORD: directusroot
MYSQL_DATABASE: directus
MYSQL_USER: directus
MYSQL_PASSWORD: directus
Optionally, Directus data folders can be mounted for persistent
storage:
volumes:
- ./data/config:/var/directus/config
- ./data/uploads:/var/directus/public/uploads
An .htaccess file can be placed in the uploads directory to
prevent PHP execution:
<IfModule mod_php7.c>
php_flag engine off
</IfModule>
Initial installation requires "install" to be called:
docker-compose up -d && docker-compose run app install
Login defined in docker-compose:
An attacker can upload a PHP file and open it at
uploads/_/originals/[randomid].php.
If a .htaccess file is used, the code does not get executed and
gets returned in plain text.
You can edit the item in Directus and change the Filename Disk
to "test/file.php" (it doesn't
matter that there is no folder named test yet, Directus/Apache does
you a
favor and creates it
for you).
Now you can access the file at
/uploads/_/originals/test/file.php.
Even if you delete the file in Directus it remains on the server,
and can
be accessed via the
above mentioned URL.
To get code execution the next step is to simply upload an own
.htaccess file containing
<IfModule mod_php7.c>
php_flag engine on
</IfModule>
And again change the Filename Disk to test/.htaccess.
Now calling /uploads/_/originals/test/file.php executes the PHP file.
Vulnerable / tested versions:
-----------------------------
The following versions have been tested and found to be vulnerable.
According to the vendor,
only the Apache-based docker image with the local-storage driver is
affected and not the
Directus suite as a whole.
* v8.4.0
* v8.8.1 (latest version at the time of the test)
It is assumed that all previous v8 versions are affected as well.
Version 9 uses a different architecture and is not affected by this vulnerability.
Vendor contact timeline:
------------------------
2020-12-16 | Contacting vendor through
2021-03-04 | Contacting vendor again through
2021-03-05 | Vendor reply, exchanged S/MIME certificates
2021-03-08 | Sending security advisory to vendor
2021-03-12 | Asking the vendor whether they received the advisory;
no reply
2021-03-25 | Asking vendor again for status update
2021-03-25 | Vendor: v8 will be fixed in new version
2021-03-26 | Vendor: the issue has been fixed in v8.8.2 available
at dockerhub
2021-04-07 | Coordinated release of security advisory
Solution:
---------
The vendor provides an updated version v8.8.2 at dockerhub which
fixes the security
issue:
https://hub.docker.com/layers/directus/directus/v8.8.2-apache/images/sha256-d9898b6442b0150c3c377b50e706757f35d2d563bd82ddaf97f3ae4ba450a6e6?context=explore
Alternatively, version 9 can be installed as well, which uses a
different
architecture
and is not affected.
Workaround:
-----------
None
Advisory URL:
-------------
https://sec-consult.com/vulnerability-lab/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SEC Consult Vulnerability Lab
SEC Consult, an Atos company
Europe | Asia | North America
About SEC Consult Vulnerability Lab
The SEC Consult Vulnerability Lab is an integrated part of SEC
Consult, an
Atos company. It ensures the continued knowledge gain of SEC
Consult in the
field of network and application security to stay ahead of the
attacker. The
SEC Consult Vulnerability Lab supports high-quality penetration
testing and
the evaluation of new offensive and defensive technologies for our
customers.
Hence our customers obtain the most current information about
vulnerabilities
and valid recommendation about the risk profile of new
technologies.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Interested to work with the experts of SEC Consult?
Send us your application https://sec-consult.com/career/
Interested in improving your cyber security with the experts of
SEC Consult?
Contact our local offices https://sec-consult.com/contact/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Mail: research at sec-consult dot com
Web: https://www.sec-consult.com
Blog: http://blog.sec-consult.com
Twitter: https://twitter.com/sec_consult
EOF O. Boehlk, M. Friedmann / @2021