The TFTP implementation on Cisco Small Business SPA30x, SPA50x, SPA51x phones 7.5.7 improperly validates firmware-image file integrity, which allows local users to load a Trojan horse image by leveraging shell access, aka Bug ID CSCut67400.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.