Coldcard entropy exploit (2026)

A build/link error in Coldcard firmware from March 2021 (Mk2/Mk3 4.0.1–4.1.9, plus affected Mk4/Mk5/Q releases) made seed generation use MicroPython's software PRNG instead of the hardware RNG. Effective seed strength fell from 128 bits to ~40 bits on Mk2/Mk3 and ~72 bits on Mk4/Q/Mk5 (Coinkite's preliminary estimates). From 30 July 2026 attackers regenerated weak seeds offline and swept single-sig wallets in several waves; the devices themselves were not hacked.

Galaxy Research (14 Aug 2026): 1,778.84 BTC (~$112.7M) confirmed stolen from 8,600+ addresses; up to 2,417.35 BTC if unconfirmed footprints and 'Wave 4' are included. Earlier tallies: 1,596 BTC confirmed / 2,055 BTC with Wave 4 (Galaxy, 3 Aug) and ~1,816 BTC (TRM, 5 Aug). 1,531 BTC sat unmoved at attacker addresses; no multisig wallet was hit. Coinkite shipped fixes: 4.2.0 (Mk2/Mk3), 5.6.0 (Mk4/Mk5), 1.5.0Q (Q), Edge 6.6.0X/6.6.0QX. Updating does not repair an old seed.