Cisco IP Phone Duplicate Key Vulnerability

A vulnerability in Cisco Unified IP Phones could allow an unauthenticated, remote attacker to impersonate another user's phone if the Cisco Unified Communications Manager (CUCM) is in secure mode. This vulnerability is due to improper key generation during the manufacturing process that could result in duplicated manufactured keys installed on multiple devices. An attacker could exploit this vulnerability by performing a machine-in-the-middle attack on the secure communication between the phone and the CUCM. A successful exploit could allow the attacker to impersonate another user's phone. This vulnerability cannot be addressed with software updates. There is a workaround that addresses this vulnerability.    This advisory is available at the following link:https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-cp6901-dup-cert-82jdJGe4

There is a workaround that addresses this vulnerability.

As a workaround for this vulnerability, install a Locally Significant Certificate (LSC):

Verify that the CUCM certificate is up to date.
Open the phone configuration page.
Navigate to Settings > Security Configuration > LSC.
Install the LSC.

See Configure LSC on Cisco IP Phone with CUCM https://www.cisco.com/c/en/us/support/docs/content-networking/certificates/213295-how-to-install-an-lsc-on-a-cisco-ip-phon.html for more details.