A flaw in Coldcard seed generation lets attackers recreate private keys from the press of a button
Coinkite warned that some Coldcard wallets may have generated weak Bitcoin seeds, putting funds at risk. Affected devices include Mk3 units made from March 2021 onward with firmware 4.0.1 or later, plus Mk4, Mk5, and Q devices before specific firmware fixes. The issue is in seed generation, before normal hardware-wallet protections like offline signing and secure storage. If an attacker can guess candidate seeds, they can derive addresses, watch for deposits, and steal funds. Because old addresses remain controlled by the original seed, fixing the problem requires creating a new wallet and moving funds on-chain. A strong BIP-39 passphrase, multisig, or user-supplied dice entropy can reduce risk, but Coinkite still recommends migration to a freshly generated seed. Users should verify backups, fingerprints, and receiving addresses, and test with a small payment first. The warning also highlights a broader custody problem: seeds can outlive devices and support channels, so durable alerts and repeatable migration procedures are necessary.
