Coldcard Firmware Flaw Exposes Thousands of Bitcoin Wallets to Attack

A vulnerability in the March 2021 Coldcard firmware release has led to a series of attacks on thousands of Bitcoin wallets. The flaw allows attackers to reproduce keys generated with weak software-based randomness, enabling them to systematically drain funds from affected accounts.

According to Galaxy Research, three distinct waves of attacks have swept nearly $89 million in losses from 4,585 addresses. Each wave appears to be the work of a single operator, but it's unclear if the same attacker is behind all three.

The latest wave targets smaller balances and uses more complex, harder-to-trace transaction patterns. The attacker has now emptied wallets worth a few thousand dollars each, with losses totaling 1,367 Bitcoin across all three waves.