{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "083838eb8e17fe5f6fcaf761bdbe203110288b0b"
            },
            {
              "fixed": "289dbdbad641943b29a3b8d1eb36506cc8cec10a"
            }
          ],
          "repo": "https://github.com/ScriptKittyOS/beam_mcp",
          "type": "GIT"
        }
      ]
    },
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0.1.0"
              },
              {
                "fixed": "0.10.1"
              }
            ],
            "source": "AFFECTED_FIELD"
          },
          "events": [
            {
              "introduced": "2add129e65d04759ce67c77520208b854c05dcee"
            },
            {
              "fixed": "04548e143256729eb2cc99690861037c5372dbe8"
            }
          ],
          "repo": "https://github.com/scriptkittyos/beam_mcp",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-mrg2-4747-fmpw"
  ],
  "database_specific": {
    "cna_assigner": "EEF",
    "cwe_ids": [
      "CWE-20"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/88xxx/CVE-2026-88257.json"
  },
  "details": "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.\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",
  "modified": "2026-10-09T02:30:36.452414805Z",
  "published": "2026-10-08T13:40:55.828Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-88257.html"
    },
    {
      "type": "WEB",
      "url": "https://github.com"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/88xxx/CVE-2026-88257.json"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ScriptKittyOS/beam_mcp"
    },
    {
      "type": "FIX",
      "url": "https://github.com/ScriptKittyOS/beam_mcp/commit/083838eb8e17fe5f6fcaf761bdbe203110288b0b"
    },
    {
      "type": "FIX",
      "url": "https://github.com/ScriptKittyOS/beam_mcp/commit/289dbdbad641943b29a3b8d1eb36506cc8cec10a"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/ScriptKittyOS/beam_mcp/security/advisories/GHSA-mrg2-4747-fmpw"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-88257"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-88257"
    },
    {
      "type": "WEB",
      "url": "https://repo.hex.pm"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "beam_mcp: nested tool argument constraints advertised but not enforced"
}