# CVE-2026-77540: Ubiquiti UniFi OS command injection vulnerability

Source: https://junglewise.ai/threats/cve-2026-77540-ubiquiti-unifi-os-command-injection-vulnerability  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-26. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-77540 · Severity: critical · CVSS 9.1 · Published 2026-08-26

UniFi OS is network management software used by organizations to configure and monitor network infrastructure devices. A vulnerability in the OS allows a privileged network-connected attacker to inject and execute arbitrary commands on the host device, potentially gaining full control of the system and the ability to modify network configurations or access sensitive data.

Technologies: [Ubiquiti UniFi OS](https://junglewise.ai/threats/technologies/unifi-os). Vendors: [Ubiquiti](https://junglewise.ai/threats/vendors/ubiquiti).

## Quick answers

**Is CVE-2026-77540 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77540 being exploited in the wild.

**How severe is CVE-2026-77540?** Critical severity, with a CVSS score of 9.1, published 26 August 2026.

**Which products and versions are affected?** Ubiquiti UniFi OS.

**Is there a fix for CVE-2026-77540?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-77540 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-77540?** Check whether you run Ubiquiti UniFi OS. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An improper input validation vulnerability in UniFi OS Server allows command injection on the host device. The vulnerability requires the attacker to have network access and high privileges to exploit it. By sending crafted input that bypasses validation checks, an attacker can inject and execute arbitrary system commands with the privileges of the UniFi OS process. This could lead to complete system compromise, unauthorized access to network credentials, or lateral movement within the network infrastructure.

## Affected products

- Ubiquiti UniFi OS

## Timeline

- 2026-08-26: disclosed

## References

- [https://community.ui.com/releases/Security-Advisory-Bulletin-067/fc4a3488-7c43-4628-8bab-f715e96dbfc9](https://community.ui.com/releases/Security-Advisory-Bulletin-067/fc4a3488-7c43-4628-8bab-f715e96dbfc9)

## Related threats

- [Ubiquiti UniFi OS CRLF injection authentication bypass](https://junglewise.ai/threats/cve-2026-77550-ubiquiti-unifi-os-crlf-injection-authentication-bypass)
- [Ubiquiti UniFi OS CRLF injection authentication bypass](https://junglewise.ai/threats/cve-2026-77549-ubiquiti-unifi-os-crlf-injection-authentication-bypass)
- [Ubiquiti UniFi OS active debug code privilege escalation](https://junglewise.ai/threats/cve-2026-77545-ubiquiti-unifi-os-active-debug-code-privilege-escalation)
- [Ubiquiti UniFi OS command injection in input validation](https://junglewise.ai/threats/cve-2026-77539-ubiquiti-unifi-os-command-injection-in-input-validation)
- [Ubiquiti UniFi OS privilege escalation in access control](https://junglewise.ai/threats/cve-2026-77536-ubiquiti-unifi-os-privilege-escalation-in-access-control)