CVE-2026-77543: UniFi Access Application RCE Vulnerability

CVE-2026-77543 Overview

CVE-2026-77543 is a command injection vulnerability in the Ubiquiti UniFi Access Application caused by improper input validation [CWE-20]. An authenticated attacker with low privileges and network access can inject and execute arbitrary operating system commands 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-adjacent attacker can achieve arbitrary command execution on the UniFi Access host, leading to full compromise of the access control system and connected physical security infrastructure.

Affected Products

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

Discovery Timeline

2026-08-26 - CVE-2026-77543 published to NVD
2026-08-26 - Last updated in NVD database

Technical Details for CVE-2026-77543

Vulnerability Analysis

The UniFi Access Application fails to properly validate user-supplied input before passing it to a system command handler. An attacker with low-privileged credentials and network reachability to the application can craft input that breaks out of the intended parameter context. The malformed input is interpreted by the underlying shell or command execution routine, resulting in arbitrary command execution on the host.

Because UniFi Access controls physical entry systems, command execution on the host can extend to unlocking doors, tampering with audit logs, and pivoting into adjacent network segments. The vulnerability carries a scope change, meaning the impact extends beyond the application's own security boundary to the host operating system and potentially connected UniFi infrastructure.

Root Cause

The root cause is improper input validation [CWE-20]. The application accepts attacker-controlled data and forwards it into a command execution path without adequate sanitization, escaping, or use of parameterized APIs. Shell metacharacters and command separators are not filtered, allowing injection of additional commands alongside the intended operation.

Attack Vector

Exploitation requires network access to the UniFi Access Application and valid low-privileged credentials. The attacker submits a crafted request to a vulnerable endpoint, embedding shell metacharacters within an input field that is later concatenated into a system command. The injected commands execute with the privileges of the UniFi Access service on the host device.

Refer to the UI Security Advisory Bulletin 067 for technical details of the vulnerable input surface.

Detection Methods for CVE-2026-77543

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 external IP addresses.
New or modified files in system directories, cron entries, or startup scripts on the UniFi Access host.
Authentication events from low-privileged UniFi Access accounts followed by unusual API activity.

Detection Strategies

Monitor process trees for shell interpreters such as sh, bash, or cmd.exe spawned by UniFi Access binaries.
Inspect UniFi Access application logs for API requests containing shell metacharacters like ;, |, &&, or backticks in input fields.
Correlate authentication events with subsequent process execution and outbound network telemetry on the host.

Monitoring Recommendations

Baseline normal UniFi Access process behavior and alert on deviations, particularly command interpreters and network utilities.
Forward host and application logs to a centralized SIEM for cross-source correlation and retention.
Review UniFi Access user account activity for privilege changes, new administrative sessions, or door control anomalies.

How to Mitigate CVE-2026-77543

Immediate Actions Required

Apply the fixed UniFi Access Application version identified in UI Security Advisory Bulletin 067 without delay.
Restrict network access to the UniFi Access Application management interface using firewall rules or VLAN segmentation.
Rotate credentials for all UniFi Access user accounts, particularly low-privileged accounts, and audit for unauthorized additions.
Review host logs and installed software for signs of prior exploitation before returning the system to normal operation.

Patch Information

Ubiquiti has released a fixed version of the UniFi Access Application. Consult UI Security Advisory Bulletin 067 for the specific patched build and upgrade guidance. Apply the update to all UniFi Access host devices in the environment.

Workarounds

Limit management interface exposure to a dedicated administrative network or VPN until the patch is applied.
Enforce strong authentication and remove unused low-privileged accounts that could be leveraged for exploitation.
Enable available application audit logging and forward events to an external log store to preserve evidence if the host is compromised.