CVE-2026-55581

mcp-shell: Secure Mode Allowlist Bypass via Default `/bin/bash` Executable

Published Aug 25, 2026 CVSS 3.1 · 8.4 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

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
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Sonirico
Sonirico mcp-shell
Vendors & Products Sonirico
Sonirico mcp-shell
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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Aug 25, 2026, 7:01 PM
Reserved
Jun 16, 2026, 11:18 PM
Status
Deferred
Published
Aug 25, 2026, 4:16 PM
Modified
Sep 9, 2026, 9:07 PM