An unauthenticated attacker who can connect to TCP port 9100 can issue a Printer Job Language (PJL) command that will crash the target device. The device will reboot, after which the attacker can reissue the command to repeatedly crash the device. A malformed PJL variable FORMLINES is set to a non number value causing the target to crash.
Credits
Stephen Fewer, Principal Security Researcher at Rapid7