{"id":"CVE-2026-88257","title":"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","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 ch…","severity":"medium","cvss":5.3,"cvssVector":"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","cwe":["CWE-20"],"vendor":"ScriptKittyOS","product":"beam_mcp","affected":["beam_mcp >= 0.1.0 < 0.10.1","scriptkittyos/beam_mcp >= 083838eb8e17fe5f6fcaf761bdbe203110288b0b < 289dbdbad641943b29a3b8d1eb36506cc8cec10a"],"published":"2026-10-08","updated":"2026-10-08","sourceUpdated":"2026-10-08T21:01:07.830","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-88257","references":[{"url":"https://cna.erlef.org/cves/CVE-2026-88257.html","label":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"},{"url":"https://github.com/ScriptKittyOS/beam_mcp/commit/083838eb8e17fe5f6fcaf761bdbe203110288b0b","label":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"},{"url":"https://github.com/ScriptKittyOS/beam_mcp/commit/289dbdbad641943b29a3b8d1eb36506cc8cec10a","label":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"},{"url":"https://github.com/ScriptKittyOS/beam_mcp/security/advisories/GHSA-mrg2-4747-fmpw","label":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-88257","label":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}],"tags":["nvd","cve.org"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-10-08T13:59:14.866448Z"},"cvssSource":"cna","ingestedAt":"2026-10-08T14:47:16.344Z","slug":"CVE-2026-88257","body":"## Overview\n\nImproper 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}