Scan MCP tool definitions for hidden injection payloads (CVE-2025-53773)
AI agents call scan_tool_definitions to retrieve information from ZugaShield without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and analyzes tool definitions to identify security vulnerabilities (injection payloads). It performs pattern matching or heuristic scanning without creating, modifying, executing code, or destroying data. The blast radius of misuse is limited—a compromised scan could produce false positives/negatives in threat detection, but cannot directly harm systems or exfiltrate sensitive data.
From the tool's definition Tool description explicitly states 'Scan MCP tool definitions' — a read-only inspection operation. The name and description indicate analysis of tool definitions to detect threats, with no modification, execution, or deletion of data.
Attacks that exploit this kind of access
Scan MCP tool definitions for hidden injection payloads (CVE-2025-53773). It is categorised as a Read tool in the ZugaShield MCP Server, which means it retrieves data without modifying state.
Register the ZugaShield MCP server in PolicyLayer and add a rule for scan_tool_definitions: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches ZugaShield. Nothing to install.
scan_tool_definitions is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the scan_tool_definitions rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for scan_tool_definitions. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
scan_tool_definitions is provided by the ZugaShield MCP server (zuga-technologies/zugashield). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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