Cisco patches critical SSRF bug in Unified Communications

Cisco has released patches for a critical vulnerability in its Unified Communications Manager (Unified CM) and Unified Communications Manager Session Management Edition (SME) products that could allow an unauthenticated attacker to gain full administrative control of affected systems. The flaw, tracked as CVE-2026-20230, is a server-side request forgery (SSRF) vulnerability.

The issue stems from improper validation of specific HTTP requests processed by the WebDialer service. An attacker could exploit this by sending a crafted HTTP request to a vulnerable device, which would allow them to write arbitrary files to the underlying operating system. Cisco warns that these files could later be used to escalate privileges to root, the highest level of system access. The company has rated the advisory as Critical due to this potential for full system compromise, despite the vulnerability's Common Vulnerability Scoring System (CVSS) base score of 8.6.

A significant mitigating factor is that the vulnerability only affects systems where the Cisco WebDialer Web Service is enabled. This service is disabled by default on all affected systems. Administrators can check the service's status by...