Coldcard Wallets Hit by Fourth Wave of Attacks, Almost 449 BTC at Risk

A fourth wave of attacks on Coldcard-generated Bitcoin wallets may be underway, according to blockchain researcher Alex Thorn. The suspected attacks could put almost 449 BTC ($62,527) at risk.

The latest activity follows three earlier waves linked to a weak-entropy vulnerability affecting certain Coldcard firmware versions released after March 2021. Thorn's analysis identified 218 transactions affecting 462 suspected victim addresses between Bitcoin blocks 960778 and 969792.

These transactions moved 388.93 BTC, valued at about $24.4 million at current rates, into 216 destination addresses. Almost all of these new addresses had no past transaction history, leading Thorn to describe them as 'LIKELY Coldcard victims.'

CoinKite, the maker of the Coldcard wallet, has confirmed that seeds created on affected Mk3, Mk4, Mk5, and Q devices are exposed. Although newer patched firmware has stopped the problem for future seeds, it cannot secure old ones.