Coldcard seed flaw exploited as attackers steal about2,000 BTC
On-chain studies estimate roughly1,816–2,100 BTC drained from more than5,200 Coldcard-derived addresses, prompting large BTC movements and migrations into multisig setups.
Deep dive
According to crypto.news, Decrypt, news.bitcoin.com and other outlets, a firmware bug in Coldcard’s seed generator, active since March2021, routed key creation through a weak software RNG. That left some seeds with roughly40–72 bits of entropy instead of128, allowing attackers to precompute vulnerable wallets and sweep them remotely in multiple waves starting July30,2026. On-chain analyses by Galaxy Research and Checkonchain now estimate1,816–2,100 BTC stolen from more than5,200 addresses, with total losses in the roughly $116M–$130M range at recent prices. Casa reports that the exploit also pushed many users—Coldcard and non-Coldcard alike—to migrate into multisig setups, while Coinkite has shipped patched firmware and urged full seed and wallet migrations.
Conclusion
Watch for final consolidated loss figures, further movements from the attacker-controlled BTC addresses, and how Coinkite and rival hardware manufacturers respond with stronger randomness testing, clearer guidance, and wider promotion of multisig for large self-custodied BTC balances.
$BTC
On-chain studies estimate roughly1,816–2,100 BTC drained from more than5,200 Coldcard-derived addresses, prompting large BTC movements and migrations into multisig setups.
Deep dive
According to crypto.news, Decrypt, news.bitcoin.com and other outlets, a firmware bug in Coldcard’s seed generator, active since March2021, routed key creation through a weak software RNG. That left some seeds with roughly40–72 bits of entropy instead of128, allowing attackers to precompute vulnerable wallets and sweep them remotely in multiple waves starting July30,2026. On-chain analyses by Galaxy Research and Checkonchain now estimate1,816–2,100 BTC stolen from more than5,200 addresses, with total losses in the roughly $116M–$130M range at recent prices. Casa reports that the exploit also pushed many users—Coldcard and non-Coldcard alike—to migrate into multisig setups, while Coinkite has shipped patched firmware and urged full seed and wallet migrations.
Conclusion
Watch for final consolidated loss figures, further movements from the attacker-controlled BTC addresses, and how Coinkite and rival hardware manufacturers respond with stronger randomness testing, clearer guidance, and wider promotion of multisig for large self-custodied BTC balances.
$BTC