Cisco Unified IP Phones 7900 devices (aka TNP phones) with software before 9.2.1 do not properly verify signatures for software images, which allows local users to gain privileges via a crafted image, aka Bug ID CSCtn65962.
https://exchange.xforce.ibmcloud.com/vulnerabilities/67743
http://www.securitytracker.com/id?1025588
http://www.securityfocus.com/bid/48075
http://www.cisco.com/en/US/products/products_security_advisory09186a0080b80111.shtml