UniFi OS Server: Improper Access Control
CVE-2026-77534 is a critical-severity improper access control vulnerability in UniFi OS Server from Ubiquiti, with a CVSS 3.1 base score of 9.9 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists version 5.1.37 as the first without the flaw, so updating UniFi OS Server to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.47% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update UniFi OS Server to 5.1.37 or a later version.
- Update Cloud Keys to 5.1.31 or a later version.
- Update Network Video Recorders to 5.1.31 or a later version.
- Read the advisory on community.ui.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Ubiquiti | UniFi OS Server | before 5.1.37 | 5.1.37 |
| Ubiquiti | Cloud Keys | before 5.1.31 | 5.1.31 |
| Ubiquiti | Network Video Recorders | before 5.1.31 | 5.1.31 |
| Ubiquiti | Enterprise Network Video Recorders | before 5.1.31 | 5.1.31 |
| Ubiquiti | Enterprise Network Attached Storage | before 5.1.31 | 5.1.31 |
| Ubiquiti | Dream Machines | before 5.1.31 | 5.1.31 |
| Ubiquiti | Enterprise Firewall Core | before 5.1.31 | 5.1.31 |
| Ubiquiti | Dream Routers | before 5.1.31 | 5.1.31 |
| Ubiquiti | Enterprise Fortress Gateway | before 5.1.31 | 5.1.31 |
| Ubiquiti | Cloud Gateways | before 5.1.31 | 5.1.31 |
| Ubiquiti | Dream Wall | before 5.1.31 | 5.1.31 |
| Ubiquiti | Express 7 | before 5.1.31 | 5.1.31 |
| Ubiquiti | Network Attached Storage | before 5.1.32 | 5.1.32 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H. Scored by CNA.
Official description
A malicious actor with access to the network and low privileges could exploit an Improper Access Control vulnerability found in certain devices running UniFi OS to escalate privileges within such UniFi OS devices or instances.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Access Control
The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
How developers prevent this class of flaw
- Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
- Compartmentalize the system to have safe areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in UniFi OS Server
- 10.0 Critical severity
- 9.0 Critical severity
- 9.0 Critical severity
- 9.1 Critical severity
- 9.1 Critical severity
- 9.9 Critical severity
Recent Improper Access Control vulnerabilities
- 9.8 Critical severity
- 9.9 Critical severity
- 9.0 Critical severity
- 9.1 Critical severity
- 8.2 High severity
- 9.1 Critical severity
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