CVE-2026-55581mcp-shell: Secure Mode Allowlist Bypass via Default `/bin/bash` Executable
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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
- 8.4 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-78, CWE-183, CWE-1188
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Aug 25, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
sonirico mcp-shell sonirico:mcp_shell (from the name) | before 0.6.0 | CNA record |
References
- https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3x-refsource-confirm
- https://github.com/sonirico/mcp-shell/pull/16x-refsource-misc
- https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09fx-refsource-misc
- https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0x-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.