Vulnerability found in digital signage system

A swathe of severe vulnerabilities was found in Tightrope Media Systems’ digital signage system.

A researcher has uncovered severe vulnerabilities in digital signage software developed by Tightrope Media Systems (TRMS) thanks to the use of a default password.

The findings were made due to a recent penetration test of the Carousel system conducted by cybersecurity researcher Drew Green.

Green’s client was making use of the software on an appliance provided by TRMS which the researcher describes as “essentially an x86 Windows 10 PC.”

The researcher decided to explore further. TRMS’s Carousel system allows users to upload “bulletins” which are the items displayed on digital signs.

The interface accepts .ZIP files for uploads, and during testing, Green was not only able to export existing, legitimate bulletins, but was also able to upload a .ZIP file containing two malicious files to Carousel.

However, the researcher came across a stumbling block when he attempted to travel to the URL of the malicious files.

“It appeared that when inserting files into this ZIP archive, the path separator for files and directories was being set to the forward-slash character (“/”) rather than the backslash character (“”),” Green said. “This caused the files I added to be discarded by the server upon upload. I was eventually able to see this clearly by opening the file in a hex editor.”

In order to overcome this barrier, all it took was for the researcher to manually change the characters in question. Green was then able to execute commands on the system via a web shell.

With access assured, the researcher uploaded a Powershell file which connected a remote shell back to his system — granting Green the ability to upload arbitrary files and remotely execute code.

Another vulnerability, CVE-2018-18931, was uncovered which allowed the researcher to bump up privileges on a user account to a local administrator, and while exploiting the bug required a system restart — something basic accounts cannot do — he was able to send a command to force a reboot and trigger the exploit.

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