FKIE_CVE-2026-104634

Vulnerability from fkie_nvd - Published: 2026-10-08 14:16 - Updated: 2026-10-08 21:01
Severity
2.3 (Low) - CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Summary
Incorrect Type Conversion or Cast vulnerability in BeamMCP.Server in ScriptKittyOS beam_mcp allows an MCP client's JSON true, false and null tool arguments to reach the host's dispatch function as the strings "true", "false" and "nil". After BeamMCP.Schema.validate/2 accepted a value as a boolean, normalize_arguments/2 passed every argument through to_json_value/1, whose atom clause converts true, false and nil to strings. A string is truthy in Elixir, so a host that tests a boolean argument, for example if args.dry_run, takes the opposite branch for false, and a guard such as confirm: false reads as set. The client controls the argument and could send true directly, so the practical impact is limited to hosts whose behaviour on false differs from their behaviour on true, and to any policy layer in front of the server that permits false but refuses true. The same normalisation applies to prompts/get arguments, which exist from 0.5.0. This issue affects beam_mcp: from 0.1.0 before 0.10.1.
References
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://cna.erlef.org/cves/CVE-2026-104634.html
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://github.com/ScriptKittyOS/beam_mcp/commit/083838eb8e17fe5f6fcaf761bdbe203110288b0b
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://github.com/ScriptKittyOS/beam_mcp/commit/289dbdbad641943b29a3b8d1eb36506cc8cec10a
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://github.com/ScriptKittyOS/beam_mcp/security/advisories/GHSA-wv7p-j6qh-3hj4
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://osv.dev/vulnerability/EEF-CVE-2026-104634
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://repo.hex.pm",
          "cpes": [
            "cpe:2.3:a:scriptkittyos:beam_mcp:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.BeamMCP.Server\u0027"
          ],
          "packageName": "beam_mcp",
          "packageURL": "pkg:hex/beam_mcp",
          "product": "beam_mcp",
          "programFiles": [
            "lib/beam_mcp/server.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.BeamMCP.Server\u0027:handle_message/2"
            },
            {
              "name": "\u0027Elixir.BeamMCP.Server\u0027:normalize_arguments/2"
            },
            {
              "name": "\u0027Elixir.BeamMCP.Server\u0027:to_json_value/1"
            }
          ],
          "repo": "https://github.com/ScriptKittyOS/beam_mcp",
          "vendor": "ScriptKittyOS",
          "versions": [
            {
              "lessThan": "0.10.1",
              "status": "affected",
              "version": "0.1.0",
              "versionType": "semver"
            }
          ]
        },
        {
          "collectionURL": "https://github.com",
          "cpes": [
            "cpe:2.3:a:scriptkittyos:beam_mcp:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.BeamMCP.Server\u0027"
          ],
          "packageName": "scriptkittyos/beam_mcp",
          "packageURL": "pkg:github/scriptkittyos/beam_mcp",
          "product": "beam_mcp",
          "programFiles": [
            "lib/beam_mcp/server.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.BeamMCP.Server\u0027:handle_message/2"
            },
            {
              "name": "\u0027Elixir.BeamMCP.Server\u0027:normalize_arguments/2"
            },
            {
              "name": "\u0027Elixir.BeamMCP.Server\u0027:to_json_value/1"
            }
          ],
          "repo": "https://github.com/ScriptKittyOS/beam_mcp",
          "vendor": "ScriptKittyOS",
          "versions": [
            {
              "lessThan": "289dbdbad641943b29a3b8d1eb36506cc8cec10a",
              "status": "affected",
              "version": "083838eb8e17fe5f6fcaf761bdbe203110288b0b",
              "versionType": "git"
            }
          ]
        }
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Incorrect Type Conversion or Cast vulnerability in BeamMCP.Server in ScriptKittyOS beam_mcp allows an MCP client\u0027s JSON true, false and null tool arguments to reach the host\u0027s dispatch function as the strings \"true\", \"false\" and \"nil\". After BeamMCP.Schema.validate/2 accepted a value as a boolean, normalize_arguments/2 passed every argument through to_json_value/1, whose atom clause converts true, false and nil to strings. A string is truthy in Elixir, so a host that tests a boolean argument, for example if args.dry_run, takes the opposite branch for false, and a guard such as confirm: false reads as set.\n\nThe client controls the argument and could send true directly, so the practical impact is limited to hosts whose behaviour on false differs from their behaviour on true, and to any policy layer in front of the server that permits false but refuses true. The same normalisation applies to prompts/get arguments, which exist from 0.5.0.\n\nThis issue affects beam_mcp: from 0.1.0 before 0.10.1."
    }
  ],
  "id": "CVE-2026-104634",
  "lastModified": "2026-10-08T21:01:07.830",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 2.3,
          "baseSeverity": "LOW",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "LOW",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "LOW",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-104634",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-10-08T13:58:26.222349Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-10-08T14:16:46.370",
  "references": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://cna.erlef.org/cves/CVE-2026-104634.html"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://github.com/ScriptKittyOS/beam_mcp/commit/083838eb8e17fe5f6fcaf761bdbe203110288b0b"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://github.com/ScriptKittyOS/beam_mcp/commit/289dbdbad641943b29a3b8d1eb36506cc8cec10a"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://github.com/ScriptKittyOS/beam_mcp/security/advisories/GHSA-wv7p-j6qh-3hj4"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-104634"
    }
  ],
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-704"
        }
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "type": "Secondary"
    }
  ]
}



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