FKIE_CVE-2026-88257

Vulnerability from fkie_nvd - Published: 2026-10-08 14:17 - Updated: 2026-10-08 21:01
Severity
5.3 (Medium) - CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Summary
Improper Input Validation vulnerability in BeamMCP.Schema in ScriptKittyOS beam_mcp allows an MCP client to reach a tool's dispatch function with arguments that violate the input schema the server advertised. BeamMCP.Schema.validate/2 checked type, required, additionalProperties, enum and numeric bounds on the top-level arguments object only. Constraints inside nested objects and on array items (items, minItems, maxItems, minLength, maxLength, pattern, nested required, enum and additionalProperties: false) were advertised by tools/list and never checked at tools/call or prompts/get, and keywords outside the enforced subset (oneOf, anyOf, $ref) were advertised and ignored. A host whose dispatch code relies on the schema it declared receives values the schema forbids, such as an out-of-range number or an undeclared key inside a nested object. What the host does with such a value decides the impact. This issue affects beam_mcp: from 0.1.0 before 0.10.1.
References
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://cna.erlef.org/cves/CVE-2026-88257.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-mrg2-4747-fmpw
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://osv.dev/vulnerability/EEF-CVE-2026-88257
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.Schema\u0027",
            "\u0027Elixir.BeamMCP.Server\u0027"
          ],
          "packageName": "beam_mcp",
          "packageURL": "pkg:hex/beam_mcp",
          "product": "beam_mcp",
          "programFiles": [
            "lib/beam_mcp/schema.ex",
            "lib/beam_mcp/server.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.BeamMCP.Schema\u0027:validate/2"
            },
            {
              "name": "\u0027Elixir.BeamMCP.Server\u0027:handle_message/2"
            }
          ],
          "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.Schema\u0027",
            "\u0027Elixir.BeamMCP.Server\u0027"
          ],
          "packageName": "scriptkittyos/beam_mcp",
          "packageURL": "pkg:github/scriptkittyos/beam_mcp",
          "product": "beam_mcp",
          "programFiles": [
            "lib/beam_mcp/schema.ex",
            "lib/beam_mcp/server.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.BeamMCP.Schema\u0027:validate/2"
            },
            {
              "name": "\u0027Elixir.BeamMCP.Server\u0027:handle_message/2"
            }
          ],
          "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": "Improper Input Validation vulnerability in BeamMCP.Schema in ScriptKittyOS beam_mcp allows an MCP client to reach a tool\u0027s dispatch function with arguments that violate the input schema the server advertised. BeamMCP.Schema.validate/2 checked type, required, additionalProperties, enum and numeric bounds on the top-level arguments object only. Constraints inside nested objects and on array items (items, minItems, maxItems, minLength, maxLength, pattern, nested required, enum and additionalProperties: false) were advertised by tools/list and never checked at tools/call or prompts/get, and keywords outside the enforced subset (oneOf, anyOf, $ref) were advertised and ignored.\n\nA host whose dispatch code relies on the schema it declared receives values the schema forbids, such as an out-of-range number or an undeclared key inside a nested object. What the host does with such a value decides the impact.\n\nThis issue affects beam_mcp: from 0.1.0 before 0.10.1."
    }
  ],
  "id": "CVE-2026-88257",
  "lastModified": "2026-10-08T21:01:07.830",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "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:N/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-2026-88257",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-10-08T13:59:14.866448Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-10-08T14:17:01.613",
  "references": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://cna.erlef.org/cves/CVE-2026-88257.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-mrg2-4747-fmpw"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-88257"
    }
  ],
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        }
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "type": "Secondary"
    }
  ]
}



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