Coldcard Vulnerability Exposes Singlesig Users While Multisig Remains Secure

• •A vulnerability in Coldcard wallets exposed singlesig users to potential theft.
• •Weakness in the random number generator compromised key generation entropy.
• •Multisig wallets provided enhanced security, preventing immediate access to funds.

On July 30, 2026, Coinkite issued a security advisory regarding a vulnerability in most Coldcard hardware wallets. The flaw was linked to a weak random number generator, compromising the entropy used for key generation. This left singlesig wallet users vulnerable to theft, as attackers could easily scan for keys tied to live balances. In contrast, multisig wallet users, particularly those using a 2-of-3 setup, were shielded from immediate risk, as a single compromised key was insufficient for access. Unchained reported that multisig provided additional fault tolerance and time for users to respond. Attackers exploited the vulnerability by scanning common derivation paths to find keys. Unchained also implemented direct-to-miner transaction submissions to mitigate risks associated with unconfirmed transactions. The situation emphasizes the importance of multisig wallets in enhancing security against such vulnerabilities.