A critical entropy bug in Coldcard hardware wallets enabled hackers to drain 594 Bitcoin — worth roughly $38 million — from users' wallets. Bitcoin developer Peter Todd responded with a stark warning: no Bitcoin is safe on single-signature wallets anymore.
The vulnerability
The bug lies in how Coldcard generates random numbers for private keys. A weak entropy source made it possible for attackers to brute-force the keys, effectively guessing them. The exploit didn't require physical access to the device in every case — remote attackers could scan the blockchain for vulnerable addresses and sweep the funds.
594 BTC drained
On-chain data shows 594 BTC moved from multiple addresses linked to Coldcard users. At current prices that's about $38 million. The theft appears to have happened over several days, with the hackers methodically targeting wallets that used the compromised entropy. It's one of the larger hardware-wallet-related heists in recent memory.
Peter Todd's warning
Todd, a longtime Bitcoin core developer, didn't mince words. He said that after this bug, relying on a single signature from any hardware wallet is too risky. He didn't name Coldcard specifically in every tweet, but the context was clear. The warning lands hard because single-sig wallets are the default for most Bitcoin users — one key, one point of failure.
What users should do
Anyone using a Coldcard — or any hardware wallet that relies on a single private key — should consider moving funds to a multisignature setup. Multisig requires multiple keys to authorize a transaction, so a single compromised device doesn't mean lost coins. The timing isn't great: the market is already jittery, and a $38 million theft doesn't help confidence.
Coldcard has not yet released a public statement about the bug or a firmware patch. Users are left waiting for an official fix while the stolen BTC sits in wallets controlled by the hackers. Whether those coins can ever be recovered is an open question.
