mcp-shell: Secure Mode Allowlist Bypass via Default `/bin/bash` Executable

{
  "id": "507a64bbccb2461647cde95809570b67611e9dcc42357c70acee50a31f2d260f",
  "url": "https://osv.dev/vulnerability/CVE-2026-55581",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "mcp-shell: Secure Mode Allowlist Bypass via Default `/bin/bash` Executable",
    "summary": "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 `, 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.",
    "evidence": "osv:CVE-2026-55581",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-55581",
      "aliases": [
        "CVE-2026-55581",
        "GHSA-3x77-wg38-92r3",
        "GO-2026-6290"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/sonirico/mcp-shell",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "df02c8c74044a950d5c085626da8de49c7551cd5"
                },
                {
                  "fixed": "f31377fce6ec31114e5a4398c0e5270552bce09f"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "0.6.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "f31377fce6ec31114e5a4398c0e5270552bce09f"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "df02c8c74044a950d5c085626da8de49c7551cd5"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v0.6.0"
                  }
                ]
              }
            }
          ],
          "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"
          }
        }
      ],
      "modified": "2026-10-28T02:30:31.015804497Z",
      "provider": "osv",
      "references": [
        "https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55581.json",
        "https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-55581",
        "https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f",
        "https://github.com/sonirico/mcp-shell/pull/16"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-1188",
          "CWE-183",
          "CWE-78"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55581.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-55581",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 498125,
  "published_at": "2026-08-25T15:40:10.992+00:00"
}