The Passkey Paradox: Security Gains, New Attack Vectors

Introduction: The Double-Edged Sword of Passkeys

Passkeys are rapidly emerging as a critical component of modern identity and access management (IAM) strategies, promising to deliver robust, phishing-resistant authentication. By leveraging WebAuthn standards and cryptographic keys, passkeys aim to eliminate passwords, significantly reducing the attack surface for common credential-based threats. Indeed, many organizations, including Microsoft Entra ID, are making passkeys their default authentication mechanism, pushing for widespread adoption across the enterprise landscape [9].

However, as with any transformative technology, the introduction of passkeys is not without its complexities and new security considerations. While they solve many legacy problems, passkeys introduce novel attack vectors and challenges that enterprise security teams must understand and proactively address. This article delves into the inherent paradox of passkeys: immense security gains coupled with emerging threats that demand sophisticated defensive strategies.

Phishing Resistance: A Core Strength

At their core, passkeys are designed to combat phishing, a persistent and pervasive threat. Unlike passwords, passkeys are tied to specific web origins and cannot be replayed on fraudulent sites. This fundamental design principle makes them highly resistant to traditional phishing campaigns that trick users into entering credentials on imposter sites. The underlying FIDO2 architecture ensures that the authentication ceremony happens directly between the user's device and the legitimate service, preventing man-in-the-middle attacks that plague password-based systems.

For enterprise environments, this means a significant reduction in the risk associated with credential theft, which often serves as the initial breach point for sophisticated attacks. The shift to passkeys aligns with the broader industry move towards phishing-resistant multi-factor authentication (MFA) and zero-trust principles.

Emerging Threat Vectors: The Passkey Paradox

Despite their phishing resistance, recent research highlights several critical attack vectors that challenge the narrative of passkeys as an unassailable security panacea:

1. Replay Attacks and Endpoint Compromise

New research from Michael Grafnetter presented at Black Hat USA 2026 demonstrated a "Pass-the-Passkey" attack. This vulnerability chain exploited how Windows recorded passkey assertions in event logs and how Microsoft Entra ID accepted their replay for up to ten minutes [6]. An attacker with privileges to read these logs, even unprivileged malware, could effectively replay a user's passkey assertion and gain unauthorized access. This attack bypasses the phishing resistance by compromising the endpoint where the passkey assertion is generated or stored, rather than directly phishing the user. The implications are significant: while the passkey itself isn't stolen, the authenticated session or assertion can be hijacked.

2. Insider Threats and Abuse Scenarios

Perhaps more insidious are the implications for insider threats and scenarios involving intimate partner abuse. Research from Cornell University highlights a critical gap: while passkeys are secure against external phishing, they can be weaponized by individuals with physical access to a device or existing credentials [7, 8].

If an abuser has access to a victim's computer and password, they could enroll their own passkey on the victim's account. This creates a persistent backdoor, allowing the abuser to regain access even after the victim changes passwords or tries to secure their account. The study revealed that current passkey management interfaces offer insufficient tools for users to detect or remediate such compromises, painting a "grim picture" for abuse survivors. For enterprises, this translates to heightened risk from disgruntled employees, off-boarded personnel, or even compromised endpoints in shared environments, where an enrolled passkey could facilitate unauthorized access long after an initial incident.

3. Social Engineering and Enrollment Exploitation

While passkeys prevent phishing for credentials, they don't entirely eliminate social engineering. Attackers may shift tactics to trick users into enrolling a passkey on a malicious device or service, or to approve an unauthorized passkey registration. This leverages the trust users place in official-looking communications or prompts. As organizations push for rapid passkey adoption, user unfamiliarity can be exploited, potentially leading to unintended passkey registrations on compromised or controlled devices [9]. The critical distinction is the shift from "phish for password" to "trick into enrolling bad passkey."

Enterprise Strategies for a Secure Passkey Future

To navigate the evolving threat landscape, enterprise security teams must adopt a multi-faceted approach to passkey deployment and management:

• Endpoint Security Reinforcement: Given the "Pass-the-Passkey" attack vector, robust endpoint detection and response (EDR), alongside stringent access controls and privileged access management (PAM), become even more critical. Preventing malware from reading event logs or system files is paramount to protecting passkey assertions.
• Device Trust and Conditional Access: Implementing strong device trust policies ensures that passkeys are only used from managed, healthy, and compliant devices. Integrating passkey authentication with conditional access policies can restrict access based on device state, location, and other risk factors. This can help mitigate risks from compromised endpoints or unauthorized passkey enrollments.
• Enhanced User Education: Training users on the nuances of passkey security is crucial. This includes educating them on how to identify legitimate passkey enrollment prompts, the importance of only registering passkeys on trusted devices, and the risks associated with physical device compromise. Organizations must also provide clear guidance on how to manage, review, and revoke enrolled passkeys.
• Comprehensive Passkey Lifecycle Management: Enterprises need a centralized system to manage the entire lifecycle of passkeys, similar to certificate management for PKI. This includes:
  • Visibility: Granular insight into all enrolled passkeys for each user, across all applications.
  • Revocation: The ability to rapidly revoke individual passkeys or all passkeys associated with a user or device, particularly during off-boarding or incident response.
  • Auditability: Detailed logging of passkey enrollment, usage, and revocation events for forensic analysis.
• Mitigating Insider Risk: Reviewing and enhancing policies around physical device access, shared workstations, and the off-boarding process is essential. For particularly sensitive accounts, additional out-of-band verification steps for passkey enrollment or changes may be warranted.
• Vendor Due Diligence: Evaluate passkey providers and relying parties for their implementation of security best practices, including protection against replay attacks, robust auditing features, and clear user management interfaces.

Conclusion: Beyond Phishing Resistance

Passkeys represent a significant leap forward in authentication security, effectively nullifying many traditional phishing attacks. However, their increasing adoption creates new attack surface areas that sophisticated adversaries and malicious insiders will inevitably probe. For enterprise security architects and IAM engineers, the challenge is to move beyond simply enabling passkeys to architecting a comprehensive security posture that accounts for the "Pass-the-Passkey" and abuse scenarios. A robust passkey strategy demands strong endpoint security, meticulous lifecycle management, proactive user education, and intelligent conditional access, ensuring that the benefits of passwordless authentication are fully realized without introducing unacceptable new risks. The paradox demands vigilance, not complacency.