Why do hardcoded credentials create the wrong trust model for MCP?

Why This Matters for Security Teams

Hardcoded credentials create a trust model that assumes the secret itself is the trusted actor. For MCP, that is a poor fit because tool calls are made by workloads, not by a stable human session, and the security decision has to happen at invocation time. Current guidance from the OWASP Non-Human Identity Top 10 and NHIMG’s research on Ultimate Guide to NHIs — Static vs Dynamic Secrets both point to the same operational issue: static secrets hide who actually initiated the action, when, and under what policy context.

That matters because MCP tool access is often chained across multiple systems, which means one leaked secret can become a reusable bearer token for broad lateral movement. Once a credential is embedded in code, config, or a server image, it also becomes difficult to bind to workload identity, enforce runtime policy, or prove revocation happened. The result is an audit gap, not just a secrets hygiene issue. NHIMG’s Guide to the Secret Sprawl Challenge shows how quickly secrets move outside intended control planes, especially in fast-moving automation environments. In practice, many security teams encounter the weakness only after a tool token has already been reused outside its intended workflow.

How It Works in Practice

The practical alternative is to treat the MCP client, agent, or workload as the identity primitive, then issue short-lived credentials only when a specific action is approved. That shifts trust away from a hardcoded secret and toward verified workload identity, token exchange, and policy evaluated at request time. NIST identity guidance, especially the NIST SP 800-63 Digital Identity Guidelines, supports the broader principle that identity assurance should be explicit and traceable rather than implied by possession of a static token.

For MCP, the security flow should look more like this:

• Authenticate the workload with a cryptographic identity, not a shared secret.
• Exchange that identity for a short-lived token scoped to one task, tool, or context.
• Evaluate policy at runtime so the tool call is allowed only if the current context matches the approved intent.
• Revoke or expire the token automatically after completion.

This model reduces blast radius because the token is not durable enough to be reused outside the task that created it. It also improves accountability because the action can be tied back to a workload, policy decision, and time window rather than a hardcoded secret copied into several environments. NHIMG’s coverage of the Gladinet Hard-Coded Keys RCE Exploitation and the Shai Hulud npm malware campaign show why hardcoded secrets are attractive targets: once discovered, they are easy to replay and hard to scope. These controls tend to break down when legacy MCP connectors only support static API keys because the protocol interface cannot enforce per-invocation token exchange.

Common Variations and Edge Cases

Tighter credential controls often increase integration overhead, requiring organisations to balance faster onboarding against stronger runtime assurance. That tradeoff is real in MCP environments where some tools were built for simple bearer-token access and cannot yet support workload identity or token exchange cleanly. Best practice is evolving, but there is no universal standard for this yet across every agentic stack.

The most common edge case is a hybrid environment where an MCP server supports both modern ephemeral access and older hardcoded integrations. In those cases, the safer pattern is to isolate legacy connectors, narrow their scope, and treat them as migration exceptions rather than normal operating mode. Another common failure mode is assuming that a secret stored in a vault is automatically safe. Storage location matters, but it does not solve the trust problem if the same long-lived credential can still be replayed by any process that finds it.

For agentic systems, the more relevant question is not “where is the secret kept?” but “what runtime context proves this workload is authorised to use this tool now?” That is where current guidance from the OWASP Top 10 for Agentic Applications 2026 and the emerging agent governance approach described in NHIMG’s OWASP Agentic Applications Top 10 becomes especially relevant. Static credentials remain common in low-maturity deployments, but they should be treated as a temporary bridge, not a trust model.

Related resources from NHI Mgmt Group

• How can organizations secure their MCP server credentials?
• Why do shared API keys create the wrong trust model for AI agents?
• Why do valid credentials still create risk in a Zero Trust model?
• Why do ephemeral credentials still leave risk in machine access models?