A sandbox escape issue was discovered in TitanHQ SpamTitan Gateway 7.07. It limits the admin user to a restricted shell, allowing execution of a small number of tools of the operating system. This restricted shell can be bypassed after changing the properties of the user admin in the operating system file /etc/passwd. This file cannot be accessed though the restricted shell, but it can be modified by abusing the Backup/Import Backup functionality of the web interface. An authenticated attacker would be able to obtain the file /var/tmp/admin.passwd after executing a Backup operation. This file can be manually modified to change the GUID of the user to 0 (root) and change the restricted shell to a normal shell /bin/sh. After the modification is done, the file can be recompressed to a .tar.bz file and imported again via the Import Backup functionality. The properties of the admin user will be overwritten and a root shell will be granted to the user upon the next successful login.
Published September 17, 2020.