Teams should provide a secondary authentication path so users can recover access without weakening the main control. In practice, that means keeping magic links or another controlled fallback available for edge cases such as a new PC, a lost device, or unsynced passkeys. The fallback should be limited, monitored, and treated as a recovery mechanism, not the primary sign-in method.
When the passkey is not on the device, what problem are teams actually solving?
The real issue is not passkey failure, it is recovery of access without turning the fallback into a weaker default. Users will lose devices, move between machines, or find that a passkey has not synced everywhere. The control objective is to preserve strong authentication for normal sign-in while still giving a bounded path back into the account.
What a good fallback should look like
A sound fallback is narrow, observable, and clearly secondary. It should exist for recovery cases such as a new laptop, a replacement phone, or a passkey that has not yet propagated, but it should not become a general bypass for convenience. The most useful patterns are workforce identity guidance on recovery flows and passkeys and controlled step-up methods that preserve assurance.
Teams should prefer recovery methods that can be challenged, rate-limited, and revoked cleanly. That means the fallback should be tied to identity proofing or an approved secondary channel, not left as an open-ended alternate login path. If the fallback cannot be monitored or expired, it stops being recovery and becomes a second primary door.
How to avoid weakening the main sign-in control
The key design decision is to separate ordinary authentication from exception handling. Normal users should continue to rely on the passkey path, while edge cases go through a recovery flow that has tighter policy, better logging, and a clear end state once the passkey is restored. Standards such as NIST SP 800-63 Digital Identity Guidelines are useful here because they distinguish authenticator strength and recovery assurance.
Fallbacks also need a lifecycle. They should be time-bounded, regularly tested, and removed once the user is back on a passkey-capable device. If teams leave recovery links, temporary codes, or alternate channels permanently active, attackers can target the weakest remaining path instead of the passkey itself.
Risk and Threat Considerations
The main risk is that a recovery option becomes easier to abuse than the passkey it is meant to support. Attackers often target account recovery, help desk processes, email links, or stale devices because those paths are less protected than the primary authenticator.
Failure mechanism: A broad fallback lets an attacker route around phishing-resistant authentication by exploiting the exception path, especially if the path is not tightly scoped, short-lived, and audited.
Impact: Account takeover becomes possible even when the passkey control is strong, which undermines the value of the primary authentication strategy and can expose sessions, data, and downstream systems.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
NIST SP 800-63, NIST SP 800-53 Rev 5 and CIS Controls v8 set the technical controls, while ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-63 | Digital Identity Guidelines | Defines authenticator assurance and recovery considerations for strong sign-in. |
| Recommendation — Use assurance and recovery guidance to keep fallback access weaker than the primary passkey path. | ||
| NIST SP 800-53 Rev 5 | IA-5 — Authenticator Management | Covers lifecycle control of authenticators and recovery material used for sign-in. |
| IA-2 — Identification and Authentication (Organizational Users) | Applies where teams must authenticate users while providing controlled recovery access. | |
| Recommendation — Manage fallback authenticators with expiration, revocation, and monitoring controls. Enforce strong user authentication and route exceptions through a separate recovery process. | ||
| CIS Controls v8 | CIS-5 — Account Management | Addresses account lifecycle and access restoration paths that can weaken authentication. |
| Recommendation — Review and constrain recovery paths so they do not bypass normal account controls. | ||
| ISO/IEC 27001:2022 | A.5.15 — Access control | Supports policy-driven access decisions for normal login and recovery exceptions. |
| Recommendation — Define recovery access rules that preserve the primary access control model. | ||
Practitioner Guidance
What to prioritize: Treat recovery design as part of the authentication architecture, not as a support afterthought. The most important question is whether a user can regain access without creating a reusable bypass for attackers.
What to verify: Confirm that the fallback is limited to named recovery cases, logged end to end, and easy to revoke once the user returns to a passkey. If the team cannot explain who can use it, how long it lasts, and how it is retired, the control is too loose.
Common mistake: Making the fallback so convenient that it becomes the preferred login path when passkeys are unavailable. A recovery path that is easier than the main path will eventually be abused as the main path.
Practitioner takeaway: Preserve the passkey as the normal route, and design the fallback so it restores access without creating a durable second authentication standard.
Related resources from NHI Mgmt Group
- How should security teams govern cloud access when users, service accounts, and workloads all hold permissions in the same environment?
- How should security teams decide between direct device permissions and group-based privileged access for users?
- How should security teams authenticate AI agents in enterprise environments?
- Why do ephemeral credentials still leave risk in machine access models?
