Vulnerability · Published Aug 26, 2026 · Assigned by Ubiquiti
CVE-2026-77539
Critical 9.1
In plain English
A critical-severity improper input validation in UniFi OS Server from Ubiquiti Inc. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.3% (higher than 70% of all known vulnerabilities).
Severity (CVSS 3.1)9.1Critical
Exploit odds (30 days)1.3%top 29.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Ubiquiti Inc | UniFi OS Server | 0 – before 5.1.37 |
Weakness: CWE-20 · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H