CVE-2026-55581
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.34%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 8.4 HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.34% probability · 27th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-78, CWE-183, CWE-1188
- Source
- security-advisories@github.com
References
- https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f
- https://github.com/sonirico/mcp-shell/pull/16
- https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0
- https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3
- https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.