{"api_version":"1","generated_at":"2026-10-27T13:48:55+00:00","cve":"CVE-2026-55581","urls":{"html":"https://cve.report/CVE-2026-55581","api":"https://cve.report/api/cve/CVE-2026-55581.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-55581","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-55581"},"summary":{"title":"mcp-shell: Secure Mode Allowlist Bypass via Default `/bin/bash` Executable","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.","state":"PUBLISHED","assigner":"GitHub_M","published_at":"2026-08-25 16:16:55","updated_at":"2026-09-09 21:07:31"},"problem_types":["CWE-78","CWE-183","CWE-1188","CWE-78 CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')","CWE-183 CWE-183: Permissive List of Allowed Inputs","CWE-1188 CWE-1188: Insecure Default Initialization of Resource"],"metrics":[{"version":"3.1","source":"security-advisories@github.com","type":"Secondary","score":"8.4","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.4,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"8.4","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":8.4,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3","name":"https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3","refsource":"134c704f-9b21-4f2e-91b3-4a467353bcc0","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f","name":"https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f","refsource":"security-advisories@github.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/sonirico/mcp-shell/pull/16","name":"https://github.com/sonirico/mcp-shell/pull/16","refsource":"security-advisories@github.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0","name":"https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0","refsource":"security-advisories@github.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-55581","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55581","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"sonirico","product":"mcp-shell","version":"affected < 0.6.0","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"55581","cve":"CVE-2026-55581","epss":"0.003400000","percentile":"0.270920000","score_date":"2026-09-10","updated_at":"2026-09-11 00:05:17"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"adp":[{"metrics":[{"other":{"content":{"id":"CVE-2026-55581","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","timestamp":"2026-08-25T19:01:36.178820Z","version":"2.0.3"},"type":"ssvc"}}],"providerMetadata":{"dateUpdated":"2026-08-25T19:01:56.083Z","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP"},"references":[{"tags":["exploit"],"url":"https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3"}],"title":"CISA ADP Vulnrichment"}],"cna":{"affected":[{"product":"mcp-shell","vendor":"sonirico","versions":[{"status":"affected","version":"< 0.6.0"}]}],"descriptions":[{"lang":"en","value":"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."}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":8.4,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-78","description":"CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-183","description":"CWE-183: Permissive List of Allowed Inputs","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-1188","description":"CWE-1188: Insecure Default Initialization of Resource","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-08-25T15:40:10.992Z","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M"},"references":[{"name":"https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3","tags":["x_refsource_CONFIRM"],"url":"https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3"},{"name":"https://github.com/sonirico/mcp-shell/pull/16","tags":["x_refsource_MISC"],"url":"https://github.com/sonirico/mcp-shell/pull/16"},{"name":"https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f","tags":["x_refsource_MISC"],"url":"https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f"},{"name":"https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0","tags":["x_refsource_MISC"],"url":"https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0"}],"source":{"advisory":"GHSA-3x77-wg38-92r3","discovery":"UNKNOWN"},"title":"mcp-shell: Secure Mode Allowlist Bypass via Default `/bin/bash` Executable"}},"cveMetadata":{"assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","assignerShortName":"GitHub_M","cveId":"CVE-2026-55581","datePublished":"2026-08-25T15:40:10.992Z","dateReserved":"2026-06-16T23:18:03.169Z","dateUpdated":"2026-08-25T19:01:56.083Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-25 16:16:55","lastModifiedDate":"2026-09-09 21:07:31","problem_types":["CWE-78","CWE-183","CWE-1188","CWE-78 CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')","CWE-183 CWE-183: Permissive List of Allowed Inputs","CWE-1188 CWE-1188: Insecure Default Initialization of Resource"],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.4,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":2.5,"impactScore":5.9}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-08-25T19:01:36.178820Z","id":"CVE-2026-55581","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"55581","Ordinal":"1","Title":"mcp-shell: Secure Mode Allowlist Bypass via Default `/bin/bash` ","CVE":"CVE-2026-55581","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"55581","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"mcp-shell: Secure Mode Allowlist Bypass via Default `/bin/bash` "}]}}}