FreePBX Command Injection: Authenticated Attackers Gain Host Access
The National Vulnerability Database has disclosed CVE-2026-40520, a critical command injection flaw in FreePBX’s api module. Versions 17.0.8 and earlier are vulnerable. Attackers with valid bearer tokens can exploit the initiateGqlAPIProcess() function by injecting backtick-wrapped commands into GraphQL mutation inputs. These commands are directly passed to shell_exec() without sanitization, allowing arbitrary code execution on the host system under the web server’s privileges. This vulnerability carries a HIGH severity rating (CVSS 7.2) and is categorized under CWE-78, indicating a command injection risk.
What This Means For You
- If your organization uses FreePBX versions 17.0.8 or prior, you must immediately patch or upgrade the api module. An authenticated attacker with existing access, even low-privileged, can leverage this to gain full command execution on your server. Audit your FreePBX instances for any unusual processes or network connections originating from the web server user.
Related ATT&CK Techniques
🛡️ Detection Rules
5 rules · 6 SIEM formats5 detection rules auto-generated for this incident, mapped to MITRE ATT&CK. Sigma YAML is free — export to any SIEM format via the Intel Bot.
Web Application Exploitation Attempt — CVE-2026-40520
Indicators of Compromise
| ID | Type | Indicator |
|---|---|---|
| CVE-2026-40520 | Command Injection | FreePBX api module version 17.0.8 and prior |
| CVE-2026-40520 | Command Injection | initiateGqlAPIProcess() function |
| CVE-2026-40520 | Command Injection | GraphQL moduleOperations mutation with backtick-wrapped commands in the module field |
Written by SCW Vulnerability Desk
Source & Attribution
| Source Platform | NVD |
| Channel | National Vulnerability Database |
| Published | April 21, 2026 at 16:16 UTC |
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