LAN attack can put some Samsung TVs in endless restart loop

Researcher finds serious remote denial-of-service vulnerability in Samsung TV firmware

By Lucian Constantin

A vulnerability in the firmware of several network-enabled Samsung TV models and possibly Blu-ray players allows potential attackers to put the vulnerable devices into an endless restart loop that requires the intervention of a technician to terminate, according to independent security researcher Luigi Auriemma.

Auriemma discovered the flaw on April 19 and published a proof-of-concept exploit on his website. The bug is located in the code that allows Samsung devices to be controlled over the local area network (LAN) through special iOS or Android applications.
Auriemma performed his tests on a D6000 Samsung TV with the latest firmware installed, but according to the Google Play description of the "Samsung Remote" app for Android, the remote control feature is supported on TV models greater or equal to LCD 650, LED 6500, PDP 6500, LCD 550, LED 5500, PDP 5500 and Blu-ray device models greater or equal to BD-Player D5300, BD-HTS D5000, BD-AVR D7000 and BD-HDD Combo D6900/8200/8500/8900.
When the remote control app tries to connect for the first time to a Samsung TV, the TV displays a dialog on the screen asking the user to allow or deny the connection, Auriemma said in his public advisory. The initial data packet is sent over port 55000 and contains several fields with details about the remote device, including its name, MAC address and IP address.
However, if the controller name field contains invalid characters or a line break, the TV enters in an endless restart loop regardless of whether the user selects allow or deny on the dialog screen, Auriemma said.
For about five seconds the TV appears to operate normally. Then the controls stop working, both on the physical panel and on the TV remote, and after five more seconds the TV reboots.
This behavior repeats indefinitely until a technician intervenes using the service mode, which is possible because of the five seconds of normal operation after each reboot, Auriemma said. "The user can avoid the exploiting of the vulnerability by pushing the EXIT button on the controller when the message with allow/deny is displayed on the screen," he said.
Even though the network remote control feature is intended for Android or iOS devices, the control packet can be sent from any network-enabled computer. In fact, Auriemma's proof-of-concept exploit is packed as an .exe file.
This means that a potential attacker only needs to obtain access to the LAN that the TV has joined, in order to attack it. This can be done either by breaking into a wireless access point or by infecting a computer on the same network with malware.
Auriemma also found a secondary bug that causes the device to crash if the MAC address field in the data packet contains an overly long string. He suspects that this is because of a buffer-overflow vulnerability, but can't confirm it because he doesn't want to damage his TV. Many buffer overflow vulnerabilities can result in arbitrary code execution.
Auriemma didn't notify Samsung about the issues he found. "I wanted to report the problems to Samsung but an email address doesn't exist for these types of bugs," the researcher said.
Samsung did not immediately return a request for comment sent via email.