Updated August 1, 2026 at 2:35 p.m. EDT: Funds controlled by seeds generated on affected firmware are at risk if the seed was created without at least 50 independent, private dice rolls and the funded wallet is not protected by a strong, unique BIP-39 passphrase.
Fixed firmware is now available for every affected model and release track:
- Mk2/Mk3: version 4.2.0 or later
- Mk4/Mk5 standard: version 5.6.0 or later
- Q standard: version 1.5.0Q or later
- Mk4/Mk5 Edge: version 6.6.0X or later
- Q Edge: version 6.6.0QX or later
Standard and Edge are separate release tracks. If you use Edge, install the fixed Edge release for your model. Do not assume an older Edge 6.x release is fixed merely because its version number is higher than the standard release.
Do not generate a new seed on any of these models until the update is installed.
Funds controlled by a seed generated on Mk2 or Mk3 version 4.0.1 (March 2021) through 4.1.9 inclusive are at risk if the seed was created without at least 50 fair, independent, private dice rolls and the funded wallet is not protected by a strong, unique BIP-39 passphrase.
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. A strong passphrase reduces the immediate exposure, but it does not repair the affected seed; passphrase users should also migrate as soon as practical.
TAPSIGNER, OPENDIME and SATSCARD are not affected by this bug as they are different codebases
The issue is present on Mk2 and Mk3 firmware versions 4.0.1 through 4.1.9 inclusive. It also affects seeds generated on Mk4 and Mk5 before standard version 5.6.0 or Edge version 6.6.0X, and on Q before standard version 1.5.0Q or Edge version 6.6.0QX. The impact on Mk4, Mk5 and Q is not as severe but is still serious.
If You Added Dice When Creating the Seed
This issue affects the device-generated entropy. It does not remove independent entropy that you supplied with dice.
On affected firmware, COLDCARD hashed the device-generated seed together with every dice roll entered through Add Dice Rolls:
- 50 to 98 independent, private rolls: the dice input alone contributed at least 128 bits of entropy.
- 99 or more independent, private rolls: the dice input contributed approximately 256 bits of entropy.
- Fewer than 50 rolls, or you do not remember: follow the migration guidance in this advisory.
If you entered at least 50 fair and independent rolls, and the rolls were not recorded or exposed, we do not consider the resulting seed at risk from this RNG issue alone.
This applies to the final seed words shown after the dice were added. If you are uncertain which words you used, how many rolls you entered, or whether the rolls were private, migrate to a new seed.
If You Used a Passphrase
If the affected seed was used with a strong, unique BIP-39 passphrase, that passphrase adds an independent barrier. The reduced seed entropy alone is not enough to reach funds in that passphrase wallet; an attacker must also discover the passphrase.
A short, common, patterned, quoted, or reused passphrase may be guessable. If that describes your passphrase, or you are uncertain about its strength, treat the funds as at risk and migrate immediately.
This means a BIP-39 passphrase, not the COLDCARD PIN. Even with a strong passphrase, migrate to a newly generated seed as soon as practical. Continue to protect the passphrase and do not enter it into a website or an untrusted device.
If the Mk2 or Mk3 Is Your Only Device
Firmware 4.2.0 allows the Mk2 and Mk3 to generate a replacement seed correctly. You do not need a newer COLDCARD to complete the migration. Updating does not repair the affected seed already stored on the device.
Using one Mk2 or Mk3 for both wallets requires carefully switching between the old and new seeds. If a second device with fixed firmware is available, use it instead. If the Mk2 or Mk3 is your only device:
- Verify the written backup and wallet fingerprint of the affected seed.
- Install firmware 4.2.0 or later and confirm the version on the device.
- On an empty Mk2 or Mk3, generate a new seed. Record and verify its backup, wallet fingerprint, and a receive address.
- Restore the affected seed and send a small test transaction to the verified address.
- Restore the new seed and confirm that its fingerprint matches and the test funds arrived.
- Restore the affected seed and move the remaining funds.
- Restore the new seed and confirm the migration. Keep the old backup until the complete balance has arrived and is confirmed.
The fixed firmware’s device-generated seed is sufficient. Dice rolls are optional and are not required to address this issue. A BIP-39 passphrase is a separate wallet-security choice; if used, back it up exactly and separately from the seed words.
Optional Dice-Only Seed on Mk2 or Mk3
After updating to version 4.2.0, users who are confident in their ability to
perform and verify a dice-only migration can create a replacement seed without
using the device’s random-number generator. This is optional; the normal New
Wallet flow is corrected in version 4.2.0.
On an empty Mk2 or Mk3 running 4.2.0, select Import Existing > Dice Rolls and
enter at least 99 independent rolls of a fair six-sided die. This dedicated
dice-only path hashes the roll sequence directly; it does not use the device’s
generator.
This is an advanced procedure. A one-device migration requires safely alternating between the old and new seeds. Before erasing either seed from the device, verify its written backup and XFP. Verify a receive address for the dice-generated wallet, restore and verify the original wallet, and send a small test transaction before moving the remainder. Keep the original backup until the entire migration is confirmed.
The dice-roll sequence is secret key material. Never photograph it, save it digitally, or enter it into a networked computer. Read the COLDCARD dice-roll method before attempting this option.
Migrate Carefully
When migrating to a new key, calm and care should be applied. Rushing a wallet migration can create a more immediate risk than the issue you are trying to address.
Seeds generated on Mk2 or Mk3 versions 4.0.1 through 4.1.9; Mk4 and Mk5 before standard version 5.6.0 or Edge version 6.6.0X; or Q before standard version 1.5.0Q or Edge version 6.6.0QX are affected unless the independent dice-entropy exception applies. Before generating a replacement seed, update Mk2 or Mk3 to version 4.2.0 or later; Mk4 and Mk5 to standard version 5.6.0 or later, or Edge version 6.6.0X or later; or Q to standard version 1.5.0Q or later, or Edge version 6.6.0QX or later:
- Confirm the fixed firmware version is installed.
- Generate a new seed on the updated COLDCARD.
- Record and verify its backup before depositing funds.
- Verify a new receive address on the COLDCARD screen.
- Send a small test transaction and confirm that the new wallet works.
- Only then move the remaining funds.
- Keep the old backup until the migration is complete and confirmed.
We are continuing to investigate. More details will follow.