CVE-2026-3959: WireMCP OS Command Injection Vulnerability

CVE-2026-3959 Overview

A command injection vulnerability has been identified in 0xKoda WireMCP up to commit 7f45f8b2b4adeb76be8c6227eefb38533fdd6b1e. The vulnerability exists within the server.tool function in the index.js file, which is part of the Tshark CLI Command Handler component. An attacker with local access can exploit improper input validation to inject arbitrary operating system commands, potentially leading to unauthorized code execution on the affected system.

Critical Impact

Local attackers can execute arbitrary OS commands through the Tshark CLI Command Handler, compromising system integrity and potentially gaining broader access to the affected host.

Affected Products

• 0xKoda WireMCP (up to commit 7f45f8b2b4adeb76be8c6227eefb38533fdd6b1e)
• WireMCP Tshark CLI Command Handler component
• Systems running vulnerable versions of the index.js file

Discovery Timeline

• 2026-03-11 - CVE-2026-3959 published to NVD
• 2026-03-12 - Last updated in NVD database

Technical Details for CVE-2026-3959

Vulnerability Analysis

This vulnerability falls under CWE-77 (Improper Neutralization of Special Elements used in a Command), commonly known as Command Injection. The flaw resides in the server.tool function within the index.js file of the WireMCP project's Tshark CLI Command Handler.

The application fails to properly sanitize user-supplied input before passing it to system shell commands. When the Tshark CLI handler processes requests, malicious input containing shell metacharacters or command separators can escape the intended command context and execute arbitrary commands with the privileges of the running process.

This vulnerability requires local access to exploit, meaning an attacker must have some level of access to the system running WireMCP. The exploit has been publicly disclosed, increasing the risk for organizations that have not yet addressed this issue. The project maintainer was notified through an issue report but has not yet responded.

Root Cause

The root cause of this vulnerability is insufficient input validation and sanitization in the server.tool function. The code directly incorporates user-controlled input into shell commands without properly escaping or validating special characters. This allows command injection through shell metacharacters such as semicolons (;), pipes (|), backticks, or command substitution syntax ($()).

Attack Vector

The attack requires local access to the system running WireMCP. An attacker can craft malicious input containing OS command sequences that, when processed by the Tshark CLI Command Handler, escape the intended command context and execute arbitrary system commands. Since the exploit is publicly available, attackers with local access can leverage documented techniques to compromise vulnerable installations.

The vulnerability mechanism involves the server.tool function accepting input that is passed to system shell execution without proper sanitization. Attackers can inject shell metacharacters to break out of the intended Tshark command and append their own commands. For detailed technical information, refer to the WireMCP Security Advisory PDF and the GitHub issue tracker.

Detection Methods for CVE-2026-3959

Indicators of Compromise

• Unusual process execution chains originating from the WireMCP Node.js process
• Unexpected shell commands or child processes spawned by index.js
• Log entries showing command-line arguments containing shell metacharacters (;, |, $(), backticks)
• Evidence of Tshark being invoked with malformed or suspicious parameters

Detection Strategies

• Monitor process creation events for unexpected child processes spawned by Node.js applications running WireMCP
• Implement command-line argument logging and alerting for shell metacharacter patterns in Tshark-related commands
• Use application-level logging to track all inputs processed by the server.tool function
• Deploy endpoint detection rules to identify command injection attack patterns

Monitoring Recommendations

• Enable verbose logging for the WireMCP application to capture all input processing
• Configure SIEM alerts for process execution anomalies involving the WireMCP runtime
• Monitor for file system changes or network connections initiated by processes descended from WireMCP
• Review the VulDB report for updated threat intelligence and indicators

How to Mitigate CVE-2026-3959

Immediate Actions Required

• Audit all deployments of WireMCP to identify vulnerable instances
• Restrict local access to systems running WireMCP to trusted users only
• Consider temporarily disabling the Tshark CLI Command Handler functionality until a patch is available
• Implement network segmentation to limit potential lateral movement from compromised hosts
• Monitor the GitHub WireMCP repository for security updates

Patch Information

WireMCP uses a rolling release model, meaning specific version numbers for affected or patched releases are not provided. At the time of CVE publication, the project maintainer had been notified through an issue report but has not yet responded. Organizations should monitor the repository for commits that address input sanitization in the server.tool function of index.js.

Workarounds

• Implement strict input validation at the application boundary before data reaches the server.tool function
• Use parameterized command execution methods instead of shell string concatenation where possible
• Deploy application-layer firewalls or input filtering to block requests containing shell metacharacters
• Run WireMCP with minimal privileges using principle of least privilege

# Example: Restrict WireMCP process permissions
# Create a dedicated low-privilege user for WireMCP
useradd -r -s /bin/false wiremcp-service

# Run WireMCP under restricted user context
su -s /bin/bash -c "node index.js" wiremcp-service

# Implement filesystem restrictions
chmod 750 /path/to/wiremcp
chown -R wiremcp-service:wiremcp-service /path/to/wiremcp