Critical severity · published Aug 26, 2026
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…
9.1
CVSS
1.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
High
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)1.3% · higher than 70% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
UO
UniFi OS Server · Ubiquiti Inc
before 5.1.37 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-77539
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-77539
community.ui.com
https://community.ui.com/releases/Security-Advisory-Bulletin-067/fc4a3488-7c43-4628-8bab-f715e96dbfc9
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