What is CVE-2026-77539?

CVE-2026-77539 is a critical-severity vulnerability in Ubiquiti Inc Unifi OS Server, classified under Improper Input Validation. CVSS score: 9.1/10. Published 2026-08-26.

How severe is CVE-2026-77539?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Improper input validation in Ubiquiti Inc Unifi OS Server

CVE-2026-77539

A malicious actor with access to the network and high privileges could exploit an Improper Input Validation vulnerability found in UniFi OS Server to execute a Command Injection on the host device.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H.

Affected products

Ubiquiti Inc Unifi Os Server

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

fe490ce8-0395-4072-90d8-2707e1bdf984

Frequently asked questions

What is CVE-2026-77539?: CVE-2026-77539 is a critical-severity vulnerability in Ubiquiti Inc Unifi OS Server, classified under Improper Input Validation. CVSS score: 9.1/10. Published 2026-08-26.
How severe is CVE-2026-77539?: Critical severity. CVSS v3 base score is 9.1 out of 10.