Description
mcp-shell is an MCP server for running shell commands securely, auditably, and on demand. Prior to 0.6.0, the default Docker security.yaml includes /bin/bash in allowed_executables, while security.go validates only the first token and checkBlockedPatternsAndCommands does not reject the shell command-mode flag -c. A caller of the shell_exec MCP tool can provide the command argument `/bin/bash -c <arbitrary-command>`, which passes validation and reaches executor.go, where parseCommand and exec.CommandContext execute the arbitrary command as mcpuser outside the intended allowlist. This issue is fixed in version 0.6.0.
Published: 2026-08-25
Score: 8.4 High
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-3x77-wg38-92r3 mcp-shell has a Secure Mode Allowlist Bypass via Default `/bin/bash` Executable
History

Tue, 25 Aug 2026 16:00:00 +0000

Type Values Removed Values Added
Description mcp-shell is an MCP server for running shell commands securely, auditably, and on demand. Prior to 0.6.0, the default Docker security.yaml includes /bin/bash in allowed_executables, while security.go validates only the first token and checkBlockedPatternsAndCommands does not reject the shell command-mode flag -c. A caller of the shell_exec MCP tool can provide the command argument `/bin/bash -c <arbitrary-command>`, which passes validation and reaches executor.go, where parseCommand and exec.CommandContext execute the arbitrary command as mcpuser outside the intended allowlist. This issue is fixed in version 0.6.0.
Title mcp-shell: Secure Mode Allowlist Bypass via Default `/bin/bash` Executable
Weaknesses CWE-1188
CWE-183
CWE-78
References
Metrics cvssV3_1

{'score': 8.4, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-08-25T15:40:10.992Z

Reserved: 2026-06-16T23:18:03.169Z

Link: CVE-2026-55581

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-25T16:16:55.470

Modified: 2026-08-25T16:16:55.470

Link: CVE-2026-55581

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses
  • CWE-1188

    Initialization of a Resource with an Insecure Default

  • CWE-183

    Permissive List of Allowed Inputs

  • CWE-78

    Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')