In a recent security advisory, Cisco has released an update patching a serious vulnerability affecting its Unified Communications Manager (UCM) platform.
The issue centers around static SSH credentials embedded within certain versions of Cisco UCM and Session Management Edition (SME). These default root account credentials are meant solely for development purposes and can’t be modified or removed by users. This also means that anyone who exploits the vulnerability could log in as root and execute arbitrary commands, potentially taking full control over the system.
The vulnerability, identified as CVE-2025-20309, has been rated a perfect 10.0 on the CVSS scale, marking it as critical. Cisco has confirmed that there are no workarounds available—meaning the only way to protect your systems is by applying the official updates. If left unpatched, this flaw could allow malicious actors to gain unauthorized remote access to affected systems, potentially leading to complete control over the device.
The affected products include specific releases of Cisco UCM and SME versions from 15.0.1.13010-1 through 15.0.1.13017-1, including certain engineering special (ES) releases.
Monitoring your logs can help detect if your systems have been exploited. Successful login attempts by the root account—especially via SSH—are clear indicators. For example, log entries like these can be a sign of compromise:
cucm1 authpriv 6 systemd: pam_unix(systemd-user:session): session opened for user root by (uid=0)
cucm1 authpriv 6 sshd: pam_unix(sshd:session): session opened for user root by (uid=0)If you have a support contract, you can download the updates directly from Cisco’s support portal. Or contact Cisco TAC for assistance with product and advisory information.
Exploiting default credentials is a common attack vector, and proper configurations, regular monitoring and timely patches are the best defense.
Fore details and the full advisory, visit Cisco’s official post here.
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