CVE-2026-104634 ScriptKittyOS CVE debrief

Who should care

Defenders and administrators of beam_mcp instances should assess exposure and prioritize remediation. They must verify inventory for beam_mcp versions 0.1.0 to 0.10.0 and implement compensating controls to restrict MCP client input. Security teams should review relevant monitoring, detection, and logs for exposed assets that need extra review.

Why it matters

The vulnerability allows MCP clients to send JSON boolean and null tool arguments as strings, potentially affecting host behavior. Defenders should assess exposure, prioritize remediation, and verify inventory for beam_mcp versions 0.1.0 to 0.10.0.

• Defenders must verify inventory for affected beam_mcp versions
• Remediation priority is high for hosts whose behavior differs between true and false
• Compensating controls are necessary to restrict MCP client input
• Exposure requires verification from official sources

Technical summary

The beam_mcp Server in ScriptKittyOS beam_mcp incorrectly converts JSON boolean and null tool arguments to strings, potentially affecting host behavior. This occurs because normalize_arguments/2 passes every argument through to_json_value/1, whose atom clause converts true, false, and nil to strings. As a result, a host that tests a boolean argument may take the opposite branch for false, and a guard such as confirm: false reads as set. The practical impact is limited to hosts whose behavior on false differs from their behavior on true.

Defensive priority

Defenders should assess exposure, prioritize remediation, and verify inventory for beam_mcp versions 0.1.0 to 0.10.0.

Recommended defensive actions

• Assess exposure and prioritize remediation for beam_mcp versions 0.1.0 to 0.10.0
• Verify inventory for affected beam_mcp versions
• Implement compensating controls to restrict MCP client input
• Review relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed

Evidence notes

The CVE record and source item provide details on the vulnerability, affected versions, and references. The issue affects beam_mcp versions from 0.1.0 to 0.10.0. Defenders should verify inventory for affected versions and prioritize remediation for hosts whose behavior differs between true and false. The CVE Program record and NIST NVD detail page offer additional information on the vulnerability.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.