CVE-2026-7220: FastlyMCP OS Command Injection Vulnerability

CVE-2026-7220 Overview

A command injection vulnerability has been identified in jackwrichards FastlyMCP up to commit 6f3d0b0e654fc51076badc7fa16c03c461f95620. This vulnerability affects the fastly-mcp.mjs file within the fastly_cli Tool component, where improper handling of the command argument allows attackers to inject arbitrary operating system commands. The vulnerability can be exploited remotely without authentication, potentially enabling attackers to execute malicious commands on the underlying system.

Critical Impact

Remote attackers can exploit this OS command injection vulnerability to execute arbitrary commands on the target system, potentially leading to complete system compromise, data exfiltration, or lateral movement within the network.

Affected Products

• jackwrichards FastlyMCP (up to commit 6f3d0b0e654fc51076badc7fa16c03c461f95620)
• FastlyMCP fastly_cli Tool component
• fastly-mcp.mjs file handler

Discovery Timeline

• 2026-04-28 - CVE-2026-7220 published to NVD
• 2026-04-29 - Last updated in NVD database

Technical Details for CVE-2026-7220

Vulnerability Analysis

This vulnerability is classified as CWE-77 (Improper Neutralization of Special Elements used in a Command), commonly known as Command Injection. The flaw exists in the fastly-mcp.mjs file of the fastly_cli Tool component, where user-supplied input passed to the command argument is not properly sanitized before being executed by the underlying operating system.

The vulnerability allows network-based attacks without requiring any privileges or user interaction. When successfully exploited, attackers can achieve limited impact on confidentiality, integrity, and availability of the affected system. The exploit has been publicly disclosed, increasing the risk of active exploitation in the wild.

FastlyMCP uses a rolling release model for continuous delivery, which means there are no discrete version numbers to identify vulnerable releases. The project maintainers were notified through a GitHub issue report but have not yet responded to the disclosure.

Root Cause

The root cause of this vulnerability is insufficient input validation and sanitization in the fastly_cli Tool component. When processing command arguments in fastly-mcp.mjs, the application fails to properly escape or validate special characters that could be interpreted as shell metacharacters. This allows an attacker to break out of the intended command context and inject additional OS commands.

The lack of input sanitization means that shell metacharacters such as semicolons (;), pipes (|), backticks, or command substitution syntax ($(...)) can be used to chain malicious commands with legitimate operations.

Attack Vector

The attack can be initiated remotely over the network. An attacker can craft a malicious request containing OS command injection payloads within the command argument parameter. The vulnerability requires no authentication or special privileges, and no user interaction is needed for exploitation.

The attack flow involves:

1. Identifying an exposed FastlyMCP instance running the vulnerable fastly_cli Tool
2. Crafting a malicious request with command injection payload in the command argument
3. Sending the request to the target system
4. The injected commands execute with the privileges of the FastlyMCP process

The vulnerability mechanism involves improper handling of user-controlled input in command execution contexts. When the fastly-mcp.mjs file processes the command argument, it passes unsanitized input directly to shell execution functions, allowing attackers to append arbitrary commands. For detailed technical information, refer to the VulDB vulnerability details and the GitHub issue tracker.

Detection Methods for CVE-2026-7220

Indicators of Compromise

• Unusual process spawning from FastlyMCP or Node.js processes, particularly shell commands like /bin/sh, /bin/bash, cmd.exe, or powershell.exe
• Presence of shell metacharacters in application logs or HTTP request parameters targeting the fastly_cli Tool
• Unexpected outbound network connections from systems running FastlyMCP
• Creation of suspicious files or modification of system configuration files by the FastlyMCP process

Detection Strategies

• Implement application-level logging to capture all command arguments passed to the fastly_cli Tool and alert on suspicious patterns
• Deploy web application firewalls (WAF) with rules to detect and block common command injection payloads
• Monitor process creation events for unusual child processes spawned by Node.js or FastlyMCP applications
• Use SentinelOne's Behavioral AI to detect anomalous command execution patterns indicative of command injection exploitation

Monitoring Recommendations

• Enable verbose logging in FastlyMCP to capture all incoming requests and command arguments for forensic analysis
• Configure SIEM rules to alert on patterns matching command injection attempts, including shell metacharacters in request parameters
• Implement file integrity monitoring on the FastlyMCP installation directory to detect unauthorized modifications
• Establish baseline behavior for FastlyMCP processes and alert on deviations such as unexpected network connections or file access

How to Mitigate CVE-2026-7220

Immediate Actions Required

• Restrict network access to FastlyMCP instances to trusted sources only using firewall rules or network segmentation
• Implement input validation at the network perimeter to filter requests containing shell metacharacters
• Consider temporarily disabling the vulnerable fastly_cli Tool functionality until a patch is available
• Monitor the FastlyMCP GitHub repository for security updates and patches

Patch Information

At the time of publication, no official patch has been released by the project maintainers. The vulnerability was reported through a GitHub issue, but the project has not yet responded. Since FastlyMCP uses a rolling release model, users should monitor the repository for commits that address this command injection vulnerability in the fastly-mcp.mjs file.

Organizations using FastlyMCP should consider:

• Checking for newer commits that may address this issue
• Implementing their own input sanitization as a temporary measure
• Evaluating alternative solutions if the project remains unpatched

Workarounds

• Implement a reverse proxy or API gateway in front of FastlyMCP that sanitizes all input parameters before forwarding requests
• Restrict access to the fastly_cli Tool functionality to authenticated and authorized users only
• Deploy the application in a sandboxed or containerized environment with minimal privileges to limit the impact of successful exploitation
• Use network-level controls to limit the commands and network destinations accessible from the FastlyMCP process

Implement input validation at the application or network layer to sanitize command arguments. This should include stripping or escaping shell metacharacters from user input. Additionally, consider running FastlyMCP with minimal system privileges and restricting its ability to spawn child processes or access sensitive resources.