UniFi OS Server - RCE (CVE-2026-34910)

CVE-2026-34910 is a critical improper input validation vulnerability affecting Ubiquiti UniFi OS Server and numerous UniFi OS devices, including UDM, UNVR, UNAS, and UCG models. A network-accessible attacker can exploit this flaw without authentication or user interaction to inject and execute arbitrary commands, potentially achieving remote code execution and compromising the confidentiality, integrity, and availability of affected systems.

CrowdSec has been tracking this vulnerability and its exploits since 29th of August 2026.

According to CrowdSec data, while opportunistic exploitation dominates, a portion of threat actors trying to exploit CVE-2026-34910 apply basic targeting methods such as port or service detection. This indicates emerging patterns of selective targeting. CrowdSec network telemetry also shows that exploitation of CVE-2026-34910 has significantly declined over the past week. Attack volumes are well below the long-term average, suggesting attackers are rapidly losing interest. The vulnerability appears to be falling out of active use across most threat landscapes.

Attackers target the /api/auth/validate-sso/..%2f..%2f..%2fproxy/users/api/v2/ucs/update/latest_package endpoint, using encoded path traversal to reach the update API. The pkg_name parameter is injected with shell commands such as nslookup, enabling unauthenticated remote command execution and out-of-band DNS callbacks.