FKIE_CVE-2026-55581

Vulnerability from fkie_nvd - Published: 2026-08-25 16:16 - Updated: 2026-08-25 19:16
Severity
8.4 (High) - CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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 <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.
References
security-advisories@github.comhttps://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f
security-advisories@github.comhttps://github.com/sonirico/mcp-shell/pull/16
security-advisories@github.comhttps://github.com/sonirico/mcp-shell/releases/tag/v0.6.0
security-advisories@github.comhttps://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3
134c704f-9b21-4f2e-91b3-4a467353bcc0https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "mcp-shell",
          "vendor": "sonirico",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.6.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "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 \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."
    }
  ],
  "id": "CVE-2026-55581",
  "lastModified": "2026-08-25T19:16:50.040",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "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"
        },
        "exploitabilityScore": 2.5,
        "impactScore": 5.9,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-55581",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-25T19:01:36.178820Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-25T16:16:55.470",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/sonirico/mcp-shell/pull/16"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-78"
        },
        {
          "lang": "en",
          "value": "CWE-183"
        },
        {
          "lang": "en",
          "value": "CWE-1188"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}



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