CVE-2026-20045 is a remote code execution vulnerability affecting multiple Cisco Unified Communications products, including Unified Communications Manager (Unified CM), Unified CM Session Management Edition, Unified CM IM & Presence Service, Cisco Unity Connection, and Cisco Webex Calling Dedicated Instance. The root cause is improper validation of user-supplied input in HTTP requests sent to the web-based management interface. An attacker can exploit this by sending specially crafted HTTP requests without any authentication, gaining initial user-level access to the underlying operating system. From there, the attacker can escalate privileges to root, effectively gaining full control over the affected device. The vulnerability affects a broad range of software versions, from 12.5(1)SU1 through 15SU3a and various 14.x and 15.x releases, indicating a wide attack surface. Cisco assigned a CVSS v3.1 base score of 8.2 (high), but the Security Impact Rating is critical due to the potential for root-level compromise. No public exploits or active exploitation have been reported yet. The vulnerability could allow attackers to disrupt communications infrastructure, intercept or manipulate voice and video traffic, or use compromised devices as pivot points for further network intrusion. The flaw is particularly dangerous because it requires no authentication or user interaction and can be triggered remotely over the network via HTTP. The affected products are widely deployed in enterprise and service provider environments, making this vulnerability a significant risk for organizations relying on Cisco Unified Communications solutions.

For European organizations, this vulnerability poses a severe threat to the confidentiality, integrity, and availability of critical communications infrastructure. Unified Communications Manager is often used for enterprise telephony, video conferencing, and messaging services, which are essential for daily business operations. Exploitation could lead to unauthorized access to sensitive communications, interception or manipulation of calls, and disruption of services. Compromise of these systems could also provide attackers with a foothold inside corporate networks, enabling lateral movement and further attacks on sensitive data or critical systems. Given the reliance on Cisco Unified Communications in sectors such as finance, healthcare, government, and telecommunications across Europe, the impact could be widespread. Additionally, disruption of communication services could affect regulatory compliance and business continuity. The ability to escalate privileges to root increases the risk of persistent and stealthy attacks. The lack of known exploits currently provides a window for mitigation, but the critical nature of the vulnerability demands urgent attention.

European organizations should immediately identify and inventory all affected Cisco Unified Communications products and versions in their environment. Apply Cisco’s security patches or updates as soon as they become available, prioritizing the affected versions listed. Until patches are deployed, restrict access to the web-based management interfaces by implementing network segmentation and firewall rules to limit exposure to trusted administrative networks only. Employ strong access controls and monitoring on management interfaces to detect and respond to suspicious activity. Disable or restrict HTTP access to management interfaces if possible, or enforce HTTPS with strong authentication mechanisms. Conduct regular vulnerability scans and penetration tests focusing on Unified Communications infrastructure. Implement network intrusion detection/prevention systems (IDS/IPS) tuned to detect exploitation attempts targeting this vulnerability. Maintain up-to-date backups and incident response plans tailored for Unified Communications systems. Educate IT and security teams about this vulnerability and the importance of rapid patching and monitoring. Consider deploying endpoint detection and response (EDR) solutions on affected devices if supported.