ScriptKittyOS beam_mcp up to 0.10.0 normalize_arguments/2 type conversion

Summaryinfo

A vulnerability was found in ScriptKittyOS beam_mcp up to 0.10.0. It has been declared as problematic. The impacted element is the function normalize_arguments/2. Such manipulation leads to type conversion. This vulnerability is referenced as CVE-2026-104634. It is possible to launch the attack remotely. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in ScriptKittyOS beam_mcp up to 0.10.0 and classified as problematic. Affected by this issue is the function normalize_arguments/2. The manipulation with an unknown input leads to a type conversion vulnerability. Using CWE to declare the problem leads to CWE-704. The product does not correctly convert an object, resource, or structure from one type to a different type. Impacted is integrity. CVE summarizes:

Incorrect Type Conversion or Cast vulnerability in BeamMCP.Server in ScriptKittyOS beam_mcp allows an MCP client's JSON true, false and null tool arguments to reach the host's dispatch function as the strings "true", "false" and "nil". After BeamMCP.Schema.validate/2 accepted a value as a boolean, normalize_arguments/2 passed every argument through to_json_value/1, whose atom clause converts true, false and nil to strings. A string is truthy in Elixir, so a host that tests a boolean argument, for example if args.dry_run, takes the opposite branch for false, and a guard such as confirm: false reads as set. The client controls the argument and could send true directly, so the practical impact is limited to hosts whose behaviour on false differs from their behaviour on true, and to any policy layer in front of the server that permits false but refuses true. The same normalisation applies to prompts/get arguments, which exist from 0.5.0. This issue affects beam_mcp: from 0.1.0 before 0.10.1.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-104634 since 10/04/2026. The exploitation is known to be easy. The attack may be launched remotely. There are known technical details, but no exploit is available.

Upgrading to version 0.10.1 eliminates this vulnerability.

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Productinfo

Vendor

• ScriptKittyOS

Name

• beam_mcp

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8
• 0.9
• 0.10.0

Website

• Product: https://github.com/ScriptKittyOS/beam_mcp/

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