They should avoid shared secrets wherever possible and use delegated authorization that preserves per-user scope and revocation. If a server cannot explain which user or workload owns which access path, the authorization model is too coarse for enterprise use.
Shared MCP servers need per-user authorization, not shared access
When multiple people use the same mcp server, the server should treat each user as a distinct authorisation subject, even if the runtime is shared. The practical requirement is simple: the server must know which user is behind each access path, and it must be able to enforce different permissions, expiry, and revocation without affecting everyone else.
That is why delegated authorization matters more than a single shared secret. A shared credential makes every request look the same, which defeats user-level accountability and makes revocation either too broad or ineffective. The safer pattern is to bind access to the user or workload that actually initiated it, then carry that scope through the session or token exchange.
For MCP, the distinction is especially important because the server is often acting as a capability broker for downstream tools and resources. If the server cannot separate one user’s authority from another’s, it cannot reliably limit what each person can do, prove who accessed what, or remove access cleanly when a role changes or an account is offboarded.
What “too coarse for enterprise use” looks like in practice
A coarse model usually shows up in one of three ways: a single token reused by multiple users, a server-side credential that silently authorizes every caller, or a proxy layer that collapses all user context before the server can make a decision. Any of these can work for a demo, but they create a shared blast radius in production and make least privilege impossible to enforce in a meaningful way.
The enterprise test is whether the server can answer three questions at decision time: who is the user, what delegated scope did they receive, and can that scope be revoked without breaking unrelated users. If the answer to any of those is “not really,” the design is relying on trust in the server operator rather than on authorization boundaries.
That is also where user-sharing becomes dangerous. Two users can appear to be using the same server, but if the access path is not user-specific, the server is effectively granting the same authority to both, regardless of business need. In that situation, permission changes become blunt, audit trails become ambiguous, and access review loses most of its value.
Design the authorization flow so the server can preserve identity and scope
The preferred pattern is delegated authorization with a clear trust chain from user to client to MCP server to downstream resource. In an HTTP-based deployment, the mcp authorization specification describes the server as a resource server that expects audience-bound tokens and avoids token passthrough, which helps preserve the boundary between one user’s delegated access and another’s.
That model gives teams a way to keep sessions narrow without forcing the server to become a general credential warehouse. It also supports operational needs such as selective revocation, short-lived access, and policy decisions that can vary by user, tool, environment, or task. For teams comparing authorisation patterns, NHIMG’s Authorisation Models Guide is useful for deciding when coarse roles are not enough and when a policy-driven model is a better fit.
Where the server uses OAuth-style delegation, the important question is not just whether the token is valid, but whether it is the right token for that user and that resource. If the same token can float across users or be replayed across contexts, the design has already lost the isolation the enterprise needs. For the protocol baseline, see Model Context Protocol: Authorization specification and the related OAuth resource metadata mechanism in RFC 9728.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP API Security Top 10 addresses the attack and risk surface, while NIST SP 800-53 Rev 5 sets the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | IA-9 — Identification and Authentication (Service and Outsourced Cryptographic Modules) | Shared MCP authorization depends on service-to-service and delegated authentication boundaries. |
| AC-6 — Least Privilege | Per-user delegated access for shared servers must keep permissions narrowly scoped. | |
| IA-5 — Authenticator Management | Shared secrets and long-lived credentials create the authorization weakness described in the question. | |
| Recommendation — Use IA-9 to bind MCP server access to the correct authenticated service or workload context. Enforce AC-6 so each MCP user receives only the minimum tool and resource access required. Apply IA-5 to rotate and retire credentials so shared MCP access does not become permanent. | ||
| OWASP API Security Top 10 | API2 — Broken Authentication | A shared-server model that cannot distinguish users creates authentication and delegation weaknesses. |
| API5 — Broken Function Level Authorization | The question is fundamentally about preventing overbroad action rights on a shared server. | |
| Recommendation — Use API2 controls to ensure each MCP request is tied to a valid, user-specific auth context. Use API5 to enforce function-level authorization instead of letting every user reach every tool. | ||
Practitioner Guidance
What to verify: Confirm that each user has a distinct delegated credential or token context, not just a shared server login. If one person’s revocation would force a platform-wide outage, the model is too blunt for multi-user production use.
Decision rule: If the server cannot preserve user identity through the authorization flow, move to a delegated model before expanding usage. Shared secrets are acceptable only in narrowly constrained internal cases where the server is not making user-specific security decisions.
What practitioners underestimate: The biggest failure mode is not only leakage, it is ambiguity. When access cannot be tied back to a specific user or workload, incident response, recertification, and least-privilege enforcement all become guesswork instead of control.
Practitioner takeaway: For shared MCP servers, the right objective is not “one server for many users,” it is “one server that can still enforce per-user authority, scope, and revocation as if each session were independent.”
Related resources from NHI Mgmt Group
- How should teams govern MCP access when multiple tenants share the same user identity?
- How should security teams handle authentication when users, digital IDs, and AI agents share the same trust model?
- How should security teams handle complex application authorization when users belong to multiple groups and policies conflict?
- How should teams handle identity when multiple people share the same AI agent interface?