CVE-2026-55581

HIGH 8.4

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

CVSS Score

8.4

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-78 CWE-183 CWE-1188
Vendor	sonirico
Product	mcp-shell
Published	Aug 25, 2026

Stay Ahead of the Next One

Get instant alerts for sonirico mcp-shell

Be the first to know when new high vulnerabilities affecting sonirico mcp-shell are published — delivered to Slack, Telegram or Discord.

Get Free Alerts → Free · No credit card · 60 sec setup

CVSS v3 Breakdown

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector

Local

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Affected Versions

sonirico / mcp-shell

< 0.6.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3 github.com: https://github.com/sonirico/mcp-shell/pull/16 github.com: https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f github.com: https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0