CVE-2026-55580
Received Received - Intake

Command Injection in mcp-shell Prior to 0.6.0

Publication date: 2026-08-25

Last updated on: 2026-08-25

Assigner: GitHub, Inc.

Description
mcp-shell is an MCP server for running shell commands securely, auditably, and on demand. Prior to 0.6.0, config.go initializes Security.Enabled to false, and when MCP_SHELL_SEC_CONFIG_FILE is unset, main.go starts the documented bare-binary deployment without a security policy. SecurityValidator.validateCommand in security.go then short-circuits and allows every command supplied to the shell_exec MCP tool, so an LLM connected over stdio can execute unrestricted OS commands as the mcp-shell process user. The README from-source installation and MCP client configuration omit MCP_SHELL_SEC_CONFIG_FILE, making the insecure state the documented default. This issue is fixed in version 0.6.0.

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Meta Information

Published
2026-08-25
Last Modified
2026-08-25
Generated
2026-08-25
AI Q&A
2026-08-25
EPSS Evaluated
N/A
NVD
CVE-2026-55580
EUVD
EUVD-2026-65550

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
sonirico mcp-shell 0.6.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-78 The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

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Executive Summary

CVE-2026-55580 is a vulnerability in mcp-shell, an MCP server for running shell commands. Prior to version 0.6.0, the software defaulted to insecure settings where security was disabled by default. This allowed unrestricted command execution via the shell_exec tool, letting an LLM connected over stdio run any OS command as the mcp-shell process user. The issue stemmed from missing or weak secure mode defaults and improper configuration.

Detection Guidance

Check if mcp-shell is running with Security.Enabled=false or if MCP_SHELL_SEC_CONFIG_FILE is unset. Inspect the process for unrestricted shell execution. Verify if the binary version is below 0.6.0.

Impact Analysis

This vulnerability allows attackers to execute arbitrary OS commands with the privileges of the mcp-shell process user. If exploited, it could lead to full system compromise, data theft, or unauthorized access. Users running vulnerable versions risk remote code execution through the MCP tool interface.

Compliance Impact

This vulnerability likely violates compliance requirements for data protection and secure processing. GDPR requires appropriate technical measures to ensure security of processing, while HIPAA mandates strict access controls and audit mechanisms. The lack of command restrictions and potential for unauthorized execution could result in non-compliance, data breaches, and regulatory penalties.

Mitigation Strategies

Upgrade mcp-shell to version 0.6.0 or later. Set MCP_SHELL_SEC_CONFIG_FILE to a valid security policy. Ensure Security.Enabled is true. Remove shell interpreters from allowlists. Block dangerous metacharacters like !.

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