CVE-2026-5621: Vale-MCP OS Command Injection Vulnerability

CVE-2026-5621 Overview

A command injection vulnerability has been identified in ChrisChinchilla Vale-MCP up to version 0.1.0. This vulnerability affects an unknown functionality within the file src/index.ts of the HTTP Interface component. By manipulating the config_path argument, an attacker with local access can inject and execute arbitrary operating system commands on the affected system.

Critical Impact

Local attackers can achieve arbitrary OS command execution by manipulating the config_path parameter, potentially leading to complete system compromise.

Affected Products

• ChrisChinchilla Vale-MCP versions up to and including 0.1.0
• HTTP Interface component (src/index.ts)

Discovery Timeline

• April 6, 2026 - CVE-2026-5621 published to NVD
• April 7, 2026 - Last updated in NVD database

Technical Details for CVE-2026-5621

Vulnerability Analysis

This vulnerability is classified as CWE-77 (Improper Neutralization of Special Elements used in a Command), commonly known as OS Command Injection. The vulnerability exists in the HTTP Interface component of Vale-MCP, specifically within the src/index.ts file. The affected code fails to properly sanitize or validate the config_path argument before incorporating it into system command execution contexts.

When user-controlled input flows into shell commands without proper sanitization, attackers can append or inject additional commands using shell metacharacters such as semicolons (;), pipes (|), command substitution ($()), or other special characters. This allows the execution of arbitrary commands with the privileges of the application process.

The exploit has been publicly disclosed and is available, increasing the risk of exploitation in the wild. The vendor was contacted about this disclosure but did not respond.

Root Cause

The root cause of this vulnerability is insufficient input validation and sanitization of the config_path parameter in the HTTP Interface component. The application appears to pass user-supplied configuration path values directly to system command execution functions without neutralizing shell-special characters. This is a common pattern when developers construct shell commands using string concatenation or template literals without considering that the input may contain malicious command sequences.

Attack Vector

Exploitation requires local access to the vulnerable system. An attacker must be able to interact with the HTTP Interface component and supply a malicious config_path value containing OS command injection payloads. The attack does not require elevated privileges, though local access and the ability to send requests to the HTTP Interface are prerequisites.

A typical attack would involve crafting a config_path value that breaks out of the expected command context and appends additional shell commands. For example, injecting shell metacharacters followed by arbitrary commands such as data exfiltration scripts, reverse shell connections, or system reconnaissance commands.

For detailed technical information about this vulnerability, see the GitHub Issue Report and the VulDB Vulnerability Entry.

Detection Methods for CVE-2026-5621

Indicators of Compromise

• Unusual command executions spawned from Node.js or the Vale-MCP application process
• Unexpected child processes or shell invocations from the HTTP Interface service
• Log entries showing config_path parameters containing shell metacharacters (;, |, $(), backticks)
• Suspicious outbound network connections from the Vale-MCP process

Detection Strategies

• Monitor process trees for unexpected child processes spawned by the Vale-MCP application
• Implement application-level logging to capture all config_path parameter values for review
• Use endpoint detection solutions to identify command injection patterns in process arguments
• Deploy file integrity monitoring on critical system files that may be targets of post-exploitation activity

Monitoring Recommendations

• Enable verbose logging for the Vale-MCP HTTP Interface component
• Configure SIEM rules to alert on shell metacharacter patterns in application logs
• Monitor for unusual process lineage where web application processes spawn shell commands
• Implement network segmentation to limit the blast radius of potential compromise

How to Mitigate CVE-2026-5621

Immediate Actions Required

• Restrict local access to systems running Vale-MCP to trusted users only
• Implement network segmentation to limit access to the HTTP Interface
• Consider disabling the Vale-MCP service if not critical until a patch is available
• Deploy application-level input validation as a compensating control

Patch Information

At the time of publication, the vendor (ChrisChinchilla) has not responded to disclosure attempts, and no official patch is available. Users should monitor the Vale-MCP repository for security updates and consider the workarounds below until an official fix is released.

Workarounds

• Implement strict input validation on the config_path parameter to allow only alphanumeric characters and expected path components
• Use allowlisting to restrict config_path values to predefined, known-good configuration file paths
• Deploy a web application firewall (WAF) or input sanitization layer in front of the HTTP Interface
• Run the Vale-MCP service in a sandboxed environment or container with minimal privileges

# Example: Restrict access to Vale-MCP service using firewall rules
# Block external access to the HTTP Interface port (adjust port as needed)
iptables -A INPUT -p tcp --dport 3000 -s 127.0.0.1 -j ACCEPT
iptables -A INPUT -p tcp --dport 3000 -j DROP

# Run Vale-MCP with reduced privileges (if using systemd)
# Add to service file: User=nobody, NoNewPrivileges=true