The Hidden Risk of Synced Passkeys: Why FIDO2 Device-Bound Passkeys are the Secure Choice

Date: 2025-11-20
Author: Kamel Elias, Technical Consultant for EMEA and APAC at Versasec

This isn’t just a minor bug, it’s a risk that could impact your entire organization.

But don’t worry. There’s a clear, secure, and manageable alternative that provides the passwordless future we all want, without the hazardous compromises. In this post, we’ll explore why synced passkeys are risky and how FIDO2 device-bound passkeys are the superior solution for any security-conscious organization.

What is a Passkey?

Let’s break it down in simple terms. As the name suggests, a passkey lets you “pass” and get into your account. It’s like a password, but instead of a “word” you’ve memorized, it’s a powerful cryptographic key that your device holds.

This “key” is actually a pair of keys:

• A Public Key, which is shared with the service you’re logging into (like your email or bank).
• A Private Key, which is stored securely and secretly on your device.

This concept is based on modern asymmetric cryptography and (PKI), it is far more secure than a password that can be stolen or guessed.

How do Passkeys secure MFA?

Passkeys are a fantastic way to achieve passwordless multi-factor authentication (MFA).
Here’s the magic: The passkey (your private key) is stored in a secure location, like the secure chip on your phone or, even better, a dedicated FIDO2 device.

When you log in, you just need to prove you’re you (with a PIN or fingerprint on the device itself). The device then performs a secure cryptographic “handshake” with the service. The private key never leaves your device. It’s fast, easy, and virtually immune to phishing.

Why are Synced Passkeys Vulnerable and Unsecure?

This brings us to the most important question. The difference is all in where that private key is stored.

• Synced Passkeys: These are stored in a cloud service (like a password manager or OS provider) and copied across all your trusted devices. This is convenient, but that convenience is its greatest weakness. Because the key exists in multiple places and must be “synced,” it creates a larger attack surface.
• Device-bound Passkeys (FIDO2): The private key is generated and stored permanently on a single, physical hardware token (like a USB token or smart card). It cannot be exported, copied, or synced.

The risk with synced passkeys isn’t just a theory. Researchers from firms like SquareX and presenters at DEF CON have already demonstrated how attackers can bypass passkey security using methods like JavaScript injection and “Signed Assertion Hijacking.” By targeting the syncing mechanism, they can potentially impersonate a user and gain access.

What is the best approach to ensure my passkeys are secure?

The research findings and recommendations are clear: FIDO2 device-bound keys are the gold standard for passkey security.

By combining a physical, uncopiable security key with a biometric multifactor or PIN, you create a powerful and truly phishing-resistant defense. The private key simply cannot be stolen from a remote server or tricked into syncing to an attacker’s device because it never leaves the hardware.

This is where vSEC:CMS comes in.

Our solution is built to help organizations deploy and manage FIDO2 hardware keys at scale. Instead of relying on vulnerable synced passkeys, vSEC:CMS allows you to issue and manage dedicated hardware devices with passkeys installed directly on them.
This approach gives you the best of both worlds:

• Rock-Solid Security: Eliminates the risks of synced passkeys.
• Centralized Management: Gives IT administrators full control over issuance, revocation, and device lifecycles.
• Full FIDO2 Power: Leverages the full capabilities of the FIDO2 standard, including bulk issuance and other extended features for your managed devices.

Your Secure, Passwordless Future

Passkeys are undeniably the future of authentication. However, how you implement them matters.
The evidence shows that while convenient, synced passkeys introduce risks that organizations cannot afford to ignore. For any team serious about security, the choice is clear: move to device-bound FIDO2 passkeys.
With vSEC:CMS, you can make this transition smoothly and confidently, giving your organization the robust, manageable, and truly secure authentication it deserves.

About Author

Kamel Elias is a Technical Consultant at Versasec, focusing on the EMEA and APAC regions. With over 10 years of experience spanning software development, security, PKI (Public Key Infrastructure), and IAM (Identity and Access Management) domains, Kamel brings deep expertise to his role. He is passionately focused on understanding the “how” and “why” behind modern cybersecurity challenges. His strong technical foundation is supported by a Master’s degree in Information Security and a comprehensive understanding of the full identity lifecycle.