How can security teams reduce passkey downgrade risk?

Why This Matters for Security Teams

Passkey downgrade risk matters because the strongest factor in phishing-resistant authentication is not the passkey itself, but the availability of weaker alternate paths. If SMS, OTP, email recovery, or help desk resets remain active, an attacker can often steer the user away from the preferred method and into a more capturable one. That makes the sign-in tree part of the attack surface, not just the authentication protocol.

Current guidance from NIST Cybersecurity Framework 2.0 still points teams toward access governance, protective safeguards, and continuous verification, but the practical lesson is sharper in identity engineering: if a weaker branch exists, it will be probed. NHIMG research on identity failure patterns shows why this mindset matters, especially in the Top 10 NHI Issues and the Ultimate Guide to NHIs, where fallback paths and weak secrets repeatedly undermine otherwise strong controls.

In practice, many security teams discover downgrade risk only after an adversary has already used a recovery flow, rather than through intentional sign-in testing.

How It Works in Practice

The core control is to make phishing-resistant authentication the only acceptable path wherever risk is high, then verify that the user experience, policy engine, and recovery model do not quietly reintroduce weaker options. That means reviewing not only the primary login branch, but also device enrollment, MFA reset, lost-device recovery, federated identity handoffs, and help desk overrides. A secure design is one where a passkey is not merely preferred, but required when access risk crosses a defined threshold.

Implementation usually combines policy and testing. Security teams can require passkeys for privileged users, sensitive applications, and high-risk sessions, then block fallback methods for those contexts. They should also validate that conditional access, session step-up, and risk scoring cannot be bypassed by account recovery workflows. The operational question is not only “is passkey enabled?” but “can the user be diverted into SMS, TOTP, or social engineering-resistant recovery when access should have been denied?”

• Disable alternate methods for high-risk apps and admin roles, not just for general users.
• Test real sign-in paths, including recovery and support-assisted resets.
• Use strong assurance policies that evaluate device, session, and identity context.
• Log and alert on fallback use so downgrade attempts are visible.

For teams building identity programs around modern threat models, the OWASP NHI Top 10 is useful for thinking about how identity controls fail when the attacker targets process gaps, not cryptography. The same logic applies here: downgrade resistance must be enforced at the policy layer, not assumed from the credential type alone. These controls tend to break down when legacy directories, outsourced service desks, or mixed federation estates still require fallback authentication for operational continuity.

Common Variations and Edge Cases

Tighter downgrade controls often increase support overhead, requiring organisations to balance phishing resistance against lockout risk and recovery complexity. That tradeoff is real, especially in environments with contractors, shared devices, regional SMS dependencies, or regulated business continuity requirements.

Best practice is evolving on how strict to be with recovery, but there is no universal standard for this yet. In some environments, a limited fallback may be acceptable for low-risk users if it is strongly monitored and never permitted for privileged actions. In others, especially where NIST Cybersecurity Framework 2.0 alignment is being used to strengthen identity assurance, the safer course is to remove weak branches entirely for sensitive access. The key is to define what counts as “phishing-resistant enough” for each access tier and then test that definition against real workflows.

One common edge case is federated sign-in. An application may accept passkeys locally, but the upstream identity provider may still allow SMS or OTP during recovery, which reintroduces downgrade risk. Another is device replacement, where a user cannot enroll a new passkey without first proving identity through weaker means. In both cases, the control must cover the full authentication lifecycle, not just the primary prompt.

Teams that want a broader identity-risk lens should also review the Ultimate Guide to NHIs for the structural issue: a secure credential does not help if the surrounding process remains easy to subvert.

Related resources from NHI Mgmt Group

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