RCE in Sonirico Mcp-Shell
CVE-2026-55581
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.
Vulnerability class: Command Injection (OS Command Injection)
CVSS v3 metric
CVSS v3 base score 8.4 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Sonirico Mcp-shell — versions < 0.6.0
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-55581?
- CVE-2026-55581 is a high-severity vulnerability in Sonirico Mcp-Shell, classified under OS Command Injection. CVSS score: 8.4/10. Published 2026-08-25.
- How severe is CVE-2026-55581?
- High severity. CVSS v3 base score is 8.4 out of 10.