The SSH implementation in Cisco StarOS before 19.3.M0.62771 and 20.x before 20.0.M0.62768 on ASR 5000 devices mishandles a multi-user public-key authentication configuration, which allows remote authenticated users to gain privileges by establishing a connection from an endpoint that was previously used for an administrator's connection, aka Bug ID CSCux22492.
http://www.securitytracker.com/id/1035062
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160218-asr