beam_mcp: nested tool argument constraints advertised but not enforced
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.
CVE-2026-88257
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-88257
beam_mcp
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
beam_mcp
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"cpes": [
"cpe:2.3:a:scriptkittyos:beam_mcp:*:*:*:*:*:*:*:*"
],
"repo": "https://github.com/ScriptKittyOS/beam_mcp",
"vendor": "ScriptKittyOS",
"modules": [
"'Elixir.BeamMCP.Schema'",
"'Elixir.BeamMCP.Server'"
],
"product": "beam_mcp",
"versions": [
{
"status": "affected",
"version": "0.1.0",
"lessThan": "0.10.1",
"versionType": "semver"
}
],
"packageURL": "pkg:hex/beam_mcp",
"packageName": "beam_mcp",
"programFiles": [
"lib/beam_mcp/schema.ex",
"lib/beam_mcp/server.ex"
],
"collectionURL": "https://repo.hex.pm",
"defaultStatus": "unaffected",
"programRoutines": [
{
"name": "'Elixir.BeamMCP.Schema':validate/2"
},
{
"name": "'Elixir.BeamMCP.Server':handle_message/2"
}
]
},
{
"cpes": [
"cpe:2.3:a:scriptkittyos:beam_mcp:*:*:*:*:*:*:*:*"
],
"repo": "https://github.com/ScriptKittyOS/beam_mcp",
"vendor": "ScriptKittyOS",
"modules": [
"'Elixir.BeamMCP.Schema'",
"'Elixir.BeamMCP.Server'"
],
"product": "beam_mcp",
"versions": [
{
"status": "affected",
"version": "083838eb8e17fe5f6fcaf761bdbe203110288b0b",
"lessThan": "289dbdbad641943b29a3b8d1eb36506cc8cec10a",
"versionType": "git"
}
],
"packageURL": "pkg:github/scriptkittyos/beam_mcp",
"packageName": "scriptkittyos/beam_mcp",
"programFiles": [
"lib/beam_mcp/schema.ex",
"lib/beam_mcp/server.ex"
],
"collectionURL": "https://github.com",
"defaultStatus": "unaffected",
"programRoutines": [
{
"name": "'Elixir.BeamMCP.Schema':validate/2"
},
{
"name": "'Elixir.BeamMCP.Server':handle_message/2"
}
]
}
]- Related CVEs
- CVE-2026-88257
Source reference:
/cveMetadata/cveId
Publisher severity
medium
Source reference: /containers/cna/metrics
- Event
- #12536 · Revision 1
- Added to Heist Feed
- Publisher date