{"id":"CVE-2026-88257","published":"2026-10-08T14:17:01.613","lastModified":"2026-10-08T21:01:07.830","description":"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.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":["CWE-20"],"vendors":[],"products":[],"references":[{"url":"https://cna.erlef.org/cves/CVE-2026-88257.html","tags":[]},{"url":"https://github.com/ScriptKittyOS/beam_mcp/commit/083838eb8e17fe5f6fcaf761bdbe203110288b0b","tags":[]},{"url":"https://github.com/ScriptKittyOS/beam_mcp/commit/289dbdbad641943b29a3b8d1eb36506cc8cec10a","tags":[]},{"url":"https://github.com/ScriptKittyOS/beam_mcp/security/advisories/GHSA-mrg2-4747-fmpw","tags":[]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-88257","tags":[]}],"exploitRefs":[{"url":"https://github.com/ScriptKittyOS/beam_mcp/commit/083838eb8e17fe5f6fcaf761bdbe203110288b0b","tags":[]},{"url":"https://github.com/ScriptKittyOS/beam_mcp/commit/289dbdbad641943b29a3b8d1eb36506cc8cec10a","tags":[]},{"url":"https://github.com/ScriptKittyOS/beam_mcp/security/advisories/GHSA-mrg2-4747-fmpw","tags":[]}],"hasPoc":true,"ai":null}