Coldcard issues Mk3 warning as experts examine $38M Bitcoin wallet drain
Coinkite warned Coldcard Mk3 users to move funds from wallets whose seed phrases were generated on affected firmware. Seeds created on Mk3 firmware 4.0.1 or later, through 5.0.3, may be at risk; Mk4, Q, and Mk5 are not affected in Coinkite’s early analysis. It advised creating a new seed on an unaffected device, verifying the backup and receive address, then testing a small transfer before moving all funds. The warning came amid investigation of a coordinated sweep of 594.48 BTC from single-signature wallets, but no public evidence links the sweep to the Mk3 issue. Analysts suggested the cause may be flawed entropy or another seed-generation weakness. One theory is that an attacker brute-forced affected wallets by searching a limited range of derivation paths, which could explain the concentration in native SegWit addresses and partial drains. Coinkite said its investigation is ongoing.
