CVE-2026-77546: UniFi Access Command Injection Vulnerability

CVE-2026-77546 Overview

CVE-2026-77546 is a command injection vulnerability in the Ubiquiti UniFi Access Application. The flaw stems from improper input validation [CWE-20] in the application. An authenticated attacker with low privileges and network access can inject operating system commands that execute on the host device. The scope change in the CVSS vector indicates that successful exploitation impacts resources beyond the vulnerable component. Ubiquiti disclosed the issue in Security Advisory Bulletin 067.

Critical Impact
A low-privileged network attacker can execute arbitrary commands on the host running UniFi Access, leading to full compromise of the access control system and lateral movement into adjacent networks.

Affected Products

Ubiquiti UniFi Access Application
Refer to UniFi Security Advisory Bulletin 067 for specific affected versions
Host devices running the vulnerable UniFi Access Application

Discovery Timeline

2026-08-26 - CVE-2026-77546 published to NVD
2026-08-26 - Last updated in NVD database

Technical Details for CVE-2026-77546

Vulnerability Analysis

CVE-2026-77546 is a command injection vulnerability caused by improper input validation in the UniFi Access Application. The application accepts input from an authenticated, low-privileged user and passes that input into a system-level operation without sufficient sanitization or filtering. Attackers can embed shell metacharacters or command separators that the underlying operating system interprets as additional commands.

Because the CVSS scope is changed, code executes with privileges or in a context that extends beyond the application boundary. This behavior indicates that the injected commands run under a higher-privileged process or interact with system resources controlled by the host, not just the UniFi Access process itself. UniFi Access manages physical door controllers and credential systems, so command execution on the host can disable access control, exfiltrate credential data, or enable persistence.

Root Cause

The root cause is improper input validation [CWE-20] in a UniFi Access Application component that constructs and executes operating system commands. The application concatenates attacker-controlled input into a command string without whitelisting characters, escaping metacharacters, or using parameterized execution APIs. The vendor advisory does not publicly enumerate the specific endpoint or parameter, but the CVSS vector confirms that authentication is required and user interaction is not.

Attack Vector

An attacker must reach the UniFi Access Application over the network and possess low-privileged credentials. The attacker submits a crafted request containing shell metacharacters in a field that the application forwards to a system command. The host executes the injected payload with the privileges of the UniFi Access process, and the scope change allows the payload to affect the wider host. The vulnerability does not require user interaction, which enables scripted, automated exploitation once credentials are obtained. No public proof-of-concept is currently listed in the enriched data.

Detection Methods for CVE-2026-77546

Indicators of Compromise

Unexpected child processes spawned by the UniFi Access Application service on the host device
Outbound network connections from the UniFi Access host to unfamiliar IP addresses or command-and-control infrastructure
Shell interpreters (sh, bash, cmd.exe) launched by the UniFi Access process tree
New user accounts, cron jobs, or scheduled tasks created on the UniFi Access host

Detection Strategies

Monitor process ancestry for the UniFi Access service and alert on any spawn of shell binaries or scripting interpreters
Inspect UniFi Access application logs for API requests containing shell metacharacters such as ;, |, &&, backticks, or $()
Correlate authentication events for low-privileged UniFi Access accounts with subsequent host-level command execution

Monitoring Recommendations

Enable command-line auditing on the UniFi Access host and forward logs to a centralized SIEM for correlation
Baseline normal outbound traffic from the UniFi Access host and alert on deviations
Track configuration changes to the UniFi Access Application and underlying operating system for unauthorized modifications

How to Mitigate CVE-2026-77546

Immediate Actions Required

Apply the fixed version of the UniFi Access Application as identified in UniFi Security Advisory Bulletin 067
Restrict network access to the UniFi Access management interface to trusted administrative networks only
Rotate credentials for all UniFi Access accounts, especially low-privileged operator accounts
Review UniFi Access accounts and remove unused or unnecessary low-privileged users

Patch Information

Ubiquiti has released a security update addressing CVE-2026-77546. Refer to UniFi Security Advisory Bulletin 067 for the fixed release version and upgrade instructions. Administrators should apply the patch through the standard UniFi update process and verify the deployed version after upgrade.

Workarounds

Segment the UniFi Access host on a dedicated management VLAN with strict firewall rules blocking untrusted sources
Enforce strong, unique passwords and multi-factor authentication where supported for all UniFi Access accounts
Disable or remove low-privileged accounts that are not required for daily operations until the patch is applied