{"id":"CVE-2026-55581","summary":"mcp-shell: Secure Mode Allowlist Bypass via Default `/bin/bash` Executable","details":"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 \u003carbitrary-command\u003e`, 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.","aliases":["GHSA-3x77-wg38-92r3","GO-2026-6290"],"modified":"2026-08-27T11:47:33.999912165Z","published":"2026-08-25T15:40:10.992Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55581.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-1188","CWE-183","CWE-78"]},"references":[{"type":"WEB","url":"https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55581.json"},{"type":"ADVISORY","url":"https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55581"},{"type":"FIX","url":"https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f"},{"type":"FIX","url":"https://github.com/sonirico/mcp-shell/pull/16"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/sonirico/mcp-shell","events":[{"introduced":"0"},{"fixed":"f31377fce6ec31114e5a4398c0e5270552bce09f"},{"fixed":"df02c8c74044a950d5c085626da8de49c7551cd5"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"0.6.0"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"versions":["v0.5.0","v0.4.0","v0.3.1","v0.3.0","v0.2.2","v0.2.0","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55581.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"}]}