The vulnerability in the implementation of ISDN functions in the Cisco IOS XE operating system for Cisco 4000 Series Integrated Services Routers allows a attacker to transmit IPv4 traffic through an unauthenticated ISDN connection for several seconds, from the initial setup of the ISDN connection until a failure in authentication of the PPP connection occurs.

The vulnerability of the Cisco IOS XE operating system’s ISDN function implementation for Cisco 4000 Series Integrated Services Routers is related to the lack of protection for service data. Exploiting this vulnerability allows a malicious actor to transmit IPv4 traffic through an unauthenticated...