CVE-2026-20230

An unauthenticated server-side request forgery (SSRF) flaw exists in Cisco Unified Communications Manager (Unified CM) and Unified CM Session Management Edition (Unified CM SME), caused by improper input validation of specific HTTP requests. An attacker triggers it by sending a crafted HTTP request to the device's WebDialer service, which must be enabled for exploitation (it is disabled by default). Successful exploitation lets the attacker write files to the underlying operating system, which can later be used to elevate privileges to root — the reason Cisco assigned a Critical Security Impact Rating despite the 8.6 (High) CVSS base score. Organizations running affected Unified CM or Unified CM SME deployments, particularly those with WebDialer enabled and reachable from untrusted networks, are exposed. The flaw is being exploited in the wild: public exploit references appeared in mid-June 2026, and CISA added it to the Known Exploited Vulnerabilities catalog on 2026-06-25, with EPSS indicating an ~88% probability of exploitation within 30 days.

What to do: Upgrade affected Unified CM and Unified CM SME deployments to the fixed release cited in Cisco's advisory (specific version not provided in this dataset), prioritizing internet-exposed systems per CISA BOD 26-04 requirements. Confirm whether the WebDialer service is enabled and disable it if unused, or restrict network access to it. Check device logs for crafted HTTP requests hitting WebDialer endpoints and unexpected file writes on the underlying OS that could indicate prior exploitation.