Cisco has released security updates to address a maximum-severity security flaw in Unified Communications Manager (Unified CM) and Unified Communications Manager Session Management Edition (Unified CM SME) that could permit an attacker to login to a susceptible device as the root user, allowing them to gain elevated privileges.
The vulnerability, tracked as CVE-2025-20309, carries a CVSS score of 10.0.
“This vulnerability is due to the presence of static user credentials for the root account that are reserved for use during development,” Cisco said in an advisory released Wednesday.
“An attacker could exploit this vulnerability by using the account to log in to an affected system. A successful exploit could allow the attacker to log in to the affected system and execute arbitrary commands as the root user.”
Hardcoded credentials like this usually come from testing or quick fixes during development, but they should never make it into live systems. In tools like Unified CM that handle voice calls and communication across a company, root access can let attackers move deeper into the network, listen in on calls, or change how users log in.
The networking equipment major said it found no evidence of the flaw being exploited in the wild, and that it was discovered during internal security testing.
CVE-2025-20309 affects Unified CM and Unified CM SME versions 15.0.1.13010-1 through 15.0.1.13017-1, irrespective of device configuration.
Cisco has also released indicators of compromise (IoCs) associated with the flaw, stating successful exploitation would result in a log entry to “/var/log/active/syslog/secure” for the root user with root permissions. The log can retrieved by running the below command from the command-line interface –
cucm1# file get activelog syslog/secure
The development comes merely days after the company fixed two security flaws in Identity Services Engine and ISE Passive Identity Connector (CVE-2025-20281 and CVE-2025-20282) that could permit an unauthenticated attacker to execute arbitrary commands as the root user.
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