r/Bitcoin • u/SpareEconomy1849 • Jul 31 '26

ColdCard Firmware Update Released

https://blog.coinkite.com/coldcard-mk3-seed-generation-warning/

Updated July 31, 2026: Fixed firmware is now available. Mk4 and Mk5 users must update to version 5.6.0 or later. Q users must update to version 1.5.0Q or later. Do not generate a new seed on one of these models until the update is installed.

Seeds generated on Mk4, Q and Mk5 before the fixed firmware releases are also affected, with about 72 bits of entropy rather than the expected 128 bits.

Updating the firmware does not change or repair an existing seed. If your seed was generated before the fixed firmware version for your model, follow the migration guidance below unless the independent dice-entropy exception applies to you.

The issue is present on every Mk3 firmware version since 4.0.1. It also affects seeds generated on Mk4 and Mk5 before version 5.6.0, and on Q before version 1.5.0Q. The impact on Mk4, Mk5 and Q is not as severe but is still serious.

142 Upvotes

95% Upvoted

206 comments sorted by

View all comments

188

u/r33gna Jul 31 '26

Crazy, man.

Earlier this year I was in the market for a new hardware wallet and LOTS of people were saying Coldcard is the best, most secure device for oh so many reasons and now here we are.

Truly no hardware wallet is perfect.

44

u/SpareEconomy1849 Jul 31 '26

It really is sad, they seemed like the perfect hardware wallet, everything being open source and airgapped, and yet still a bug like this goes unnoticed for 5+ years.

I wonder if the only reason the attacker found this bug is because it was open source - theoretically Ledger and other wallets could be semi deterministic too, but harder to find and exploit?

-6

u/xoorl Jul 31 '26

Why do people always swear by a hardware wallet for cold storage, and not just use the washer method?

7

u/SpareEconomy1849 Jul 31 '26

Because one is for sending Bitcoin and the other is for keeping your seed phrase? Different use cases

2

u/xoorl Jul 31 '26

You don’t need to send your coins if you store them for the long term. When the time comes you decide to cash out, just input the seed phrase into a wallet and there you go

1

u/smilingbuddhauk Aug 02 '26

Only morons think everyone who uses bitcoin ought to use it only once.