Coldcard releases new firmware to enhance security; affected users need to regenerate their mnemonic phrases and migrate their assets

Coldcard has released the latest firmware 5.6.1 (Mk4/Mk5) and 1.5.1Q (Q). This update is based on a three-week security review following an emergency fix, focusing on addressing the security risks posed by previous mnemonic phrase generation attacks. Each newly generated mnemonic phrase must include at least one user entropy source, such as irregular key presses at least 65 times, physical dice rolls 50 times, or physical coin tosses 128 times, combined with fresh entropy provided by STM32 TRNG, SE1, and SE2.

The new firmware also adds pre-signing phased PSBT verification, strengthens USB connection and firmware update boundaries, improves Delta Mode isolation mechanisms, fixes active wallet backup issues, enhances random number generator initialization and fault checking, adjusts SIGHASH default settings, and includes multiple security and correctness improvements. Coldcard states that this update aims to further reduce the risk of the device being attacked.

The official reminder is that updating the firmware cannot fix existing mnemonic phrases generated by previously affected firmware. If a user's mnemonic phrase falls within the scope of this security announcement, they should first update the device, then generate and verify a brand new mnemonic phrase, and migrate funds to the new wallet. Coldcard recommends that all Mk4, Mk5, and Q users update their devices promptly and verify the signatures of the downloaded firmware.