A new vulnerability, dubbed "EUCLEAK," has been discovered in FIDO devices utilizing Infineon's SLE78 security microcontroller. This flaw allows attackers to potentially extract sensitive Elliptic Curve Digital Signature Algorithm (ECDSA) secret keys, leading to device cloning.
This vulnerability, uncovered by security researcher Thomas Roche of NinjaLab, leverages a side-channel attack that can retrieve ECDSA secret keys through electromagnetic (EM) acquisition. While the attack requires specialized equipment, extended physical access, and a deep understanding of electronics and cryptography, it presents a significant security risk for vulnerable devices.
Who's at Risk?
While the technical hurdles involved significantly mitigate the general risk, the potential for exploitation by highly skilled, state-sponsored threat actors targeting high-value targets remains a concern. This makes EUCLEAK less of a threat to average users, even those using theoretically vulnerable devices.
Specific Devices Affected
The EUCLEAK vulnerability specifically impacts YubiKey 5 Series devices running firmware versions older than 5.7.0, which utilize Infineon's flawed cryptographic library. The affected models include:
YubiKey 5 Series versions prior to 5.7
YubiKey 5 FIPS Series prior to 5.7
YubiKey 5 CSPN Series prior to 5.7
YubiKey Bio Series versions prior to 5.7.2
Security Key Series all versions prior to 5.7
YubiHSM 2 versions prior to 2.4.0
YubiHSM 2 FIPS versions prior to 2.4.0
Yubico, the manufacturer of the YubiKey, has rated the issue as moderate, assigning a CVSS score of 4.9, reflecting its low risk due to the attack's complexity. The company also notes that attackers would still require the user's PIN or biometric verification for complete exploitation, further hindering successful attacks.
Mitigation and Prevention
YubiKey users can check their security key's firmware version using YubiKey Manager or YubiKey Authenticator. Unfortunately, upgrading to the latest firmware versions (5.7.0 for YubiKey and 2.4.0 for YubiHSM) is not possible for vulnerable devices.
To mitigate the risk, Yubico recommends:
Using RSA signing keys instead of ECC signing keys: This shifts the reliance away from the vulnerable ECDSA algorithm.
Limiting the maximum session duration from identity provider settings: This necessitates more frequent FIDO authentications, reducing the potential window for exploitation.
Beyond YubiKey: A Wider Impact
The EUCLEAK vulnerability extends beyond YubiKey devices, affecting various products and technologies utilizing Infineon's SLE78 microcontroller:
Infineon TPMs (SLB96xx): Employed for secure boot, authentication, and cryptographic operations in smart enclaves of older (2013-2018) Samsung and OnePlus smartphones and tablets, as well as dated (mid-2010s) laptops from Lenovo, Acer, Dell, HP, and LG.
Infineon's Optiga Trust M security microcontroller: Used in a range of IoT devices.
Feitian A22 JavaCard: Employed in smart cards and authentication systems.
Other potentially impacted devices include e-passports, cryptocurrency hardware wallets (cold wallets), and any FIDO device utilizing the Infineon SLE78 microcontroller.
Implications and Future Considerations
EUCLEAK highlights the ongoing challenge of ensuring robust security in the face of evolving attack techniques. While the attack's complexity and required resources make it less likely to affect everyday users, the vulnerability's broad impact on various devices underscores the need for vigilance and proactive security measures.
This incident serves as a reminder that even seemingly secure devices can be vulnerable to sophisticated attacks. Moving forward, it is crucial for device manufacturers, security researchers, and users alike to remain informed, adopt best practices, and continuously adapt to evolving security threats.
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