Running Cisco's VoIP manager? Four words you don't want to hear: 'Backdoor SSH root key'

Cisco has warned Unified Communications installations can be remotely hijacked by miscreants, thanks to a hardwired SSH private key.

In an advisory, the networking giant said unauthenticated attackers can log into its Unified Communications Domain Manager (Unified CDM) software as a root-level user by exploiting a default SSH key meant for Cisco support reps. The key is embedded in the software, and can be extracted by reverse engineering the Unified CDM's binary.

"This will allow the attacker to connect by using the support account to the system without requiring any form of authentication," Cisco warned.

"An exploit could allow the attacker to gain access to the system with the privileges of the root user."

The vulnerability is said to be present in all versions of Cisco Unified CDM prior to version 4.4.2. The Unified CDM is part of a package Cisco and OEMs offer for large-scale enterprise and service-provider unified communications systems. It's used to manage VoIP, corporate chat and similar things at big outfits.

Dr Johannes Ullrich of the Sans Institute said that the SSH flaw poses a particular threat as it leaves attackers with a backdoor to access vulnerable networks.

"Having the same key on all systems is mistake number one, but wouldn't be fatal if the secret key would have been tugged away in Cisco's special safe deposit box," Ullrich explained.

"Instead, they left the secret key on customer systems as well. So in other words: If you own one of the systems, you got the key to access all of them."

Ullrich advises that companies make sure their Unified CDM software is updated with a patch from Cisco, and in the meantime the flaw can be mitigated by filtering SSH access to at-risk systems.

The remaining two flaws in the advisory include an elevation of privilege vulnerability in the administration GUI, and a data manipulation vulnerability that could allow an attacker to remotely tamper with some user account settings. Those flaws can also be remedied by updating to the latest version of Unified CDM. ®