Security researchers have uncovered a vulnerability in certain YubiKey 5 models that theoretically allows for cloning, but experts suggest the real-world risk remains low for most users.
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| A close-up of a YubiKey 5C security key, illustrating the hardware affected by the recently discovered vulnerability |
The Vulnerability
Researchers at NinjaLab identified a side-channel attack that exploits a cryptographic flaw in the Infineon SLE78 microcontroller used in YubiKey 5 devices. This vulnerability potentially affects millions of users who rely on these keys for multi-factor authentication to secure sensitive accounts.
Affected Devices
The following YubiKey products with firmware versions prior to 5.7 are impacted:
- YubiKey 5 Series
- YubiKey 5 FIPS Series
- YubiKey 5 CSPN Series
- YubiKey Bio Series (prior to 5.7.2)
- Security Key Series
- YubiHSM 2 (prior to 2.4.0)
The Attack: Sophisticated and Resource-Intensive
While the vulnerability is concerning, exploiting it requires:
- Physical possession of the YubiKey
- Specialized equipment (oscilloscope)
- Advanced technical knowledge
- Significant time and resources
NinjaLab estimates the cost of the necessary equipment at approximately $10,000, with high-end setups potentially reaching $40,000.
Yubico's Response
Yubico has acknowledged the vulnerability and released updated firmware (version 5.7 and newer) that addresses the issue. However, due to the tamper-resistant nature of the keys, existing devices cannot be patched.
Should You Be Worried?
Despite the vulnerability, security experts emphasize that using a YubiKey still provides significantly stronger protection than relying solely on passwords. The sophisticated nature of the attack makes it unlikely to be a widespread threat for most users.
What Users Should Do
- Check your YubiKey version using the Yubico Authenticator app
- If using an affected model, consider upgrading to a newer version for critical applications
- Continue using your YubiKey, as it still offers strong protection against common attack vectors
Broader Implications
The discovered vulnerability may extend beyond YubiKeys to other devices using the Infineon SLE78 microcontroller, including electronic passports and cryptocurrency hardware wallets. Further research is ongoing to determine the full scope of the issue.
While the YubiKey 5 vulnerability is a reminder that no security solution is perfect, it also highlights the importance of ongoing security research and the value of hardware-based authentication in creating robust defense layers.