The vulnerability lies in an unvalidated command argument in fastly-mcp.mjs of the fastly_cli tool, allowing an attacker to inject arbitrary operating system commands. This classic OS command injection can lead to full compromise of the host executing the tool, giving remote execution of any command and potentially granting full system control. The weakness is categorized under CWE‑77 and CWE‑78, indicating improper command argument handling and unsanitized shell execution.

All releases of jackwrichards' FastlyMCP up to the commit 6f3d0b0e654fc51076badc7fa16c03c461f95620 are vulnerable. The project employs a rolling release model, so affected versions span the current codebase until an update is published. The tool in question (fastly_cli) is the impacted component, and no earlier versions are known to be unaffected.

The CVSS score of 6.9 places the issue in a moderate severity bucket, and the EPSS score of 1%. The vulnerability is not listed in CISA's KEV catalog, indicating no known widely‑publicized exploits. However, the description states the attack can be initiated remotely, implying that an adversary could potentially exploit the injection from a network or remote session if the tool is exposed. Given the lack of patch and public disclosure, the risk remains real for any system running the vulnerable tool.