# CVE-2026-55581

## Summary

- **CVE ID:** CVE-2026-55581
- **Severity:** HIGH
- **CVSS Score:** 8.4 (CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** CWE-78, CWE-183, CWE-1188
- **Published:** Aug 25, 2026
- **Last Modified:** Aug 25, 2026

## 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.

## Affected Products

- sonirico — mcp-shell (< 0.6.0)

## References

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

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.34%
- **EPSS Percentile:** 27.1

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-12._