🚨 Security Flaw in YubiKey 5 Discovered: The Danger of Physical Manipulation

Researchers have uncovered a cryptographic vulnerability in the YubiKey 5 security token, which is widely used for two-factor authentication. This flaw allows attackers to clone the token if they can gain brief physical access to it.

🔑 Affected Devices

All YubiKey 5 models with firmware versions before 5.7 (released in May 2024) are affected. Unfortunately, a firmware update is not possible, meaning the vulnerable keys remain permanently at risk.

💡 How Does the Attack Work?

The attack leverages a “side-channel attack,” where an attacker measures tiny differences in computation time during the authentication process. These data points can be used to extract the token’s secret key. To execute this attack, the device must be physically opened.

⚠️ What Does This Mean?

An attacker could gain access to protected accounts if they clone the token and also possess the associated password. Since firmware updates are not available, all affected devices will remain permanently vulnerable. This underscores the importance of using multi-factor authentication (MFA).

➡️ What Should You Do?

1. Check your YubiKey’s firmware version. Users can verify their YubiKey’s version using the Yubico Authenticator app (link in comments). The model and series will be displayed in the top left corner of the app’s home screen.
2. Use additional protective measures like PIN, fingerprint, or facial recognition (MFA).
3. Do not leave your YubiKey unattended.
4. Mark or label your YubiKey case to make replication harder for attackers.

✅ Yubico recommends that users always maintain physical control over their YubiKeys. If a YubiKey is lost or stolen, immediately unregister it from all services or accounts and ensure that alternative authentication methods are set up. Ideally, every service should have two or more YubiKeys for backup and recovery scenarios. The keys can still be used safely and remain highly resistant to phishing.

🛡️ Best Practice for FIDO Authentication

Despite this flaw, FIDO-compliant authentication remains one of the most robust methods for securing accounts, as it is resistant to phishing and man-in-the-middle attacks. As long as your key doesn’t fall into the hands of a highly skilled and well-equipped attacker, it continues to be one of the safest authentication methods.

Are you a YubiKey fan, or do you rely on other trusted two-factor authentication methods? Let us know in the comments! ⬇️