MCP security is the work of protecting an AI application, its MCP clients and servers, their connections, credentials, and data as one system. The Model Context Protocol is an integration protocol—not a security boundary. A scanner can flag risky server metadata, configuration, or dependencies, but it cannot prove a server is safe or make the model’s decisions trustworthy. Effective protection combines review and scanning with least privilege, isolation, runtime authorization, and monitoring.
What MCP security covers
An MCP server can expose tools, resources, or prompts to an AI host through a client connection. When the host uses a tool, it may act with permissions granted by the user or deployment. That makes security a property of the whole connection and execution path, not just the server package.
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Local stdio connections and remote Streamable HTTP connections have different exposure profiles: a local server may run with access to the machine and files available to its process, while a remote server introduces a network endpoint and authentication concerns. OWASP describes the older HTTP+SSE transport as deprecated. Check the current MCP specification and implementation documentation before relying on transport-specific configuration details.
The model may encounter instructions or misleading content in tool names, descriptions, parameter schemas, resources, and tool results. Those inputs can influence what it asks a tool to do, but they should not be treated as trusted policy. Authorization belongs in trusted application or server code, where it can be enforced regardless of the model’s interpretation.
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Common MCP attacks and failure modes
| Attack or weakness | What happens |
|---|---|
| Tool poisoning | Instructions hidden in tool names, descriptions, parameter schemas, or returned content try to redirect the model or shape a tool call. |
| Rug pulls | A server changes its advertised tool definitions after they have been reviewed or approved. A metadata hash can reveal a definition change, but cannot detect changed code or behavior behind an unchanged schema. |
| Tool shadowing and cross-server escalation | Because connected servers’ definitions can share the model’s context, a malicious server may try to influence how the model uses another server’s tools. |
| Prompt injection through context or outputs | A retrieved page, file, or tool result contains instructions that attempt to override the user’s intent or prompt the model to take an unsafe action. Filtering may flag suspicious text, but cannot establish that all remaining content is safe. |
| Confused deputy and over-scoped access | A server uses broad authority it possesses on behalf of a request that should have been limited to a narrower identity, resource, or action. |
| Supply-chain compromise and shadow servers | Unreviewed packages, dependencies, startup commands, version drift, or unmanaged deployments introduce code or access that is not accounted for. |
| Unsafe execution, SSRF, and data egress | Model-influenced arguments reach shell commands, filesystem paths, or URL fetchers and can cause unintended execution, access to internal services, or data transfer. |
| Weak telemetry and context over-sharing | Incomplete logs make activity difficult to reconstruct, while shared or persistent context can expose information across tasks or agents. |
| Token and authorization failures | Shared, long-lived, or exposed credentials and weak authentication or authorization let a tool or caller act beyond its intended identity and scope. |
OWASP’s MCP Top 10 groups these risks into ten categories: token mismanagement and secret exposure; privilege escalation via scope creep; tool poisoning; software supply-chain attacks and dependency tampering; command injection and execution; prompt injection via contextual payloads; insufficient authentication and authorization; lack of audit and telemetry; shadow MCP servers; and context injection and over-sharing. OWASP describes the project as a living document in beta/pilot, so treat it as a security framework—not a measured ranking of incident frequency or severity.
How to scan and review MCP servers
Scanning is most useful when it starts with an accurate inventory and ends in controls that do not depend on the model to enforce them. Apply the following review to local and remote servers, including developer-installed or otherwise unmanaged instances.
- Inventory every server and connection. Record the owner, configured command or endpoint, transport, version, exposed tools, credentials, data access, and consuming clients. Include servers installed outside the organization’s normal deployment process.
- Vet the source and launch path. Review the source repository and maintainers, package provenance, requested permissions, dependencies, exact startup command, and whether the server is vendor-hosted or internally operated. Pin an exact version or image digest rather than using a floating
latestreference. - Inspect tool definitions. Review each tool name, description, parameter, and return schema. Look for irrelevant or hidden instructions, unexpectedly broad capabilities, weakly constrained strings, unusual destinations, and changes from the reviewed definition. OWASP names
mcp-scanas one example of a tool for detecting poisoned descriptions and cross-server shadowing; treat its output as a signal for investigation, not a safety guarantee. - Run conventional software checks. Use dependency and software-composition analysis on server code, scan configuration and secrets, and review command construction, file operations, URL fetching, authentication, authorization, session isolation, and error handling. MCP metadata checks do not replace these code and dependency checks.
- Test inside containment. Use a disposable environment or restricted container or virtual machine, with limited filesystem mounts, no production credentials, and only the network access required for the test. Isolate suspicious or untrusted servers; a production agent with broad access is not an appropriate scanner test harness.
- Enforce runtime controls outside the model. Validate inputs and outputs, deny by default, and explicitly allow tools and arguments. Require confirmation that shows the full parameters before destructive, financial, data-sharing, or external-network actions. Use server-side authorization and application policy rather than relying on prompts to prevent an action.
- Monitor and rescan changes. Centralize logs outside the agent’s control and record identity, session, tool call, and resulting action without recording secret values. Alert on new servers, unusual destinations, credential-file reads, bulk access, and changed definitions. Repeat relevant checks after version, dependency, configuration, permission, or schema changes.
What a scanner can—and cannot—establish
A metadata scanner can help find suspicious descriptions or patterns such as cross-server shadowing. Dependency analysis can surface known vulnerable or risky components, and configuration and secret scans can catch additional problems. These checks cover different parts of the system; no single result answers whether a server’s code, deployment, outputs, or model interactions are safe.
A clean static scan does not prove benign runtime behavior, prevent unsafe model interpretation, or replace authorization. A definition hash detects changes to the definition it covers, not altered server code or concealed behavior behind an unchanged definition. Treat findings as leads to review and remediation, and use runtime enforcement, least privilege, containment, and monitored approvals as independent safeguards.
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When assessing scanning approaches, compare what they inspect—configuration, metadata, dependencies, or runtime traffic—as well as how they fit local development and CI, how they handle data, how reports support remediation, and how regularly checks are updated. A scanner that reports a risk but cannot enforce policy is not a substitute for controls in trusted code.
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