On March 5, the hardware wallet provider Trezor disclosed a potential vulnerability in its older Cryptoasset wallet model. While this is primarily a "theoretical" attack, it could affect users who have purchased the device from a third-party.

The vulnerability was discovered after Trezor's competitor, Ledger, announced the issue. On March 6, Ledger provided more details on how this attack works. Ledger's Donjon security team used a physical supply chain attack technique to test the security of the Trezor Safe 3 - the wallet model launched in 2023 - and confirmed that the device still poses a security risk.

Attack targeting the microcontroller of Trezor Safe 3

According to Trezor, the attack exploits a weakness in the microcontroller - the processing chip that handles user interactions and transaction signing - using a "voltage glitching" technique. If an attacker has physical access to the device, they can disassemble the microcontroller, precisely modify the voltage to deceive the device, and then extract data from the memory. This could allow hackers to install malware, reveal the Seed Phrase, and steal the Cryptoassets inside the wallet.

However, Trezor claims that this attack does not affect most of its products, including the Trezor Safe 5, Trezor Model One, and Model T. Additionally, executing this attack requires advanced skills and a specialized environment, making it an unlikely widespread threat. Therefore, Trezor does not require Safe 3 users to take immediate action, especially if the device was purchased from an official source.

Security measures on new Trezor models

To mitigate the risk, Trezor has integrated a "passphrase" feature - an additional password not stored on the device - to enhance the security of wallet backups. Furthermore, the company has implemented advanced protection layers, such as firmware integrity checks. Notably, the Trezor Safe 5 model uses an STM32U5 microcontroller that is resistant to voltage glitching, helping to limit the risk of physical attacks.

The security vulnerability in Trezor Safe 3 serves as a reminder that even hardware wallets are not immune to physical threats. Users are advised to only purchase devices from official sources and always enable additional security features to protect their Cryptoassets.