CVE-2026-54674 in FreePBX
Summary
by MITRE • 09/28/2026
FreePBX is an open source IP PBX. Prior to versions 16.0.39 and 17.0.7, users authenticated via User Control Panel (UCP) are able to execute arbitrary commands on the PBX as the webserver user (typically asterisk) using specially crafted HTTP strings. Authenticated access to UCP is required. Note that this is often more common for less-privileged users to have UCP access vs. the Administrator Control Panel (ACP) access (which is usually FreePBX higher-level administrator accounts only). Insufficient sanitization of certain URL parameters utilized by UCP did not fully account for malicious strings in these fields. This could result in binaries being executed on the host server by carefully chaining commands. This issue has been patched in versions 16.0.39 and 17.0.7.
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Analysis
by VulDB Data Team • 09/28/2026
The vulnerability identified within FreePBX, specifically affecting versions prior to 16.0.39 and 17.0.7, represents a critical server-side command injection flaw located in the User Control Panel interface. This open-source IP PBX solution is widely deployed for managing telephony services, making it an attractive target for attackers seeking to compromise communication infrastructure. The core technical flaw stems from insufficient sanitization of specific URL parameters utilized by the UCP module. When users interact with this panel, input fields are not adequately validated or escaped before being processed by backend scripts that construct system commands. This lack of rigorous input validation allows specially crafted HTTP strings containing malicious payloads to bypass existing security checks and be interpreted as executable code rather than benign data.
The operational impact of this vulnerability is severe due to the privilege level under which the web server typically operates. In many standard FreePBX deployments, the Apache or Nginx processes run with elevated privileges, often associated with the asterisk user account. Consequently, an attacker who successfully authenticates via the User Control Panel can execute arbitrary commands on the host server as this privileged user. This capability enables the execution of binaries and scripts directly on the underlying operating system. The severity is further compounded by the fact that UCP access is frequently granted to less-privileged users compared to the Administrator Control Panel, which is usually restricted to high-level administrators. Therefore, a compromise through the User Control Panel can serve as an initial foothold for lateral movement or privilege escalation within the network environment.
From a threat modeling perspective, this vulnerability aligns with CWE-78 Improper Neutralization of Special Elements used in an OS Command and CWE-200 Exposure of Sensitive Information to an Unauthorized Actor if sensitive data is exfiltrated during exploitation. In terms of offensive security frameworks such as MITRE ATT&CK, the attack vector corresponds to T1059 Command and Scripting Interpreter for executing commands via web application interfaces and potentially T1068 Exploitation for Privilege Escalation depending on the specific payload used. The requirement for authentication means this is not a remote unauthenticated exploit but rather an authenticated injection that leverages trusted user sessions to bypass perimeter defenses, highlighting the risk of insider threats or compromised low-level accounts being utilized for deeper system compromise.
Mitigation strategies must prioritize immediate patching as recommended by the vendor. Organizations running FreePBX versions earlier than 16.0.39 and 17.0.7 should upgrade to these patched releases without delay to address the input sanitization deficiencies in the User Control Panel module. In addition to software updates, administrators should enforce strict access controls on UCP functionality, ensuring that only necessary personnel have permissions to use this interface. Implementing Web Application Firewalls with rules specifically designed to detect and block command injection patterns can provide an additional layer of defense against exploitation attempts. Regular auditing of user accounts and their associated privileges is also essential to minimize the attack surface available for authenticated attackers seeking to leverage these vulnerabilities for unauthorized system access.