Attack Chain

1. An attacker identifies a vulnerable instance of FastlyMCP running a version up to commit 6f3d0b0e654fc51076badc7fa16c03c461f95620.
2. The attacker crafts a malicious HTTP request targeting the fastly-mcp.mjs file.
3. The malicious request includes a manipulated command argument containing OS command injection payloads.
4. The FastlyMCP application processes the request, passing the attacker-controlled command argument to an underlying OS command execution function without proper sanitization.
5. The injected OS command is executed by the server with the privileges of the FastlyMCP application.
6. The attacker gains arbitrary code execution on the server, enabling further malicious activities.
7. The attacker may then establish persistence via web shells or by modifying system configurations.
8. Ultimately, the attacker achieves complete control over the system, potentially leading to data theft, service disruption, or further lateral movement within the network.

Impact

Successful exploitation of CVE-2026-7220 allows attackers to execute arbitrary OS commands on the affected system. This can lead to full system compromise, potentially resulting in data breaches, service disruption, and lateral movement to other systems within the network. The lack of specific versioning information due to the rolling release model makes identifying and patching vulnerable instances challenging, potentially increasing the number of victims.

Recommendation

• Monitor web server logs for suspicious requests targeting fastly-mcp.mjs with unusual parameters in the query string to detect potential exploitation attempts (see the Sigma rule Detect FastlyMCP Command Injection Attempt).
• Implement input validation and sanitization for the command argument in fastly-mcp.mjs to prevent command injection, though patching is preferable.
• Deploy the Sigma rule Detect Suspicious Process Execution via FastlyMCP to identify potential malicious process execution originating from FastlyMCP.