General coldcard seguridad hardware-wallet

What happened with Coldcard: seed-generation flaw and what to do if you are affected

Coinkite confirmed an entropy flaw in seed generation on certain Coldcard firmware versions. What is known, who is affected, what to do — plus free help if you are worried about your own setup.

Satoshi Team ·

Executive summary

Coinkite confirmed a flaw in how certain Coldcard firmware versions generate wallet seeds, reducing the entropy of the resulting keys and, in some cases, making them guessable without physical access to the device. Multiple outlets reported growing theft figures as more affected addresses were identified — Coinkite's own advisory does not publish a loss figure. If you generated a seed on affected firmware without at least 50 independent private dice rolls, you should migrate to a new seed.

What happened (timeline)

  • July 30, 2026 — Coinkite publishes its initial security advisory. The same day, several outlets report a large-scale draining of Coldcard wallets; The Hacker News cites Galaxy Research's tracking of a first wave of roughly 1,082 BTC (about $70M at the time) drained from ~1,196 addresses in about 41 minutes.
  • Following days — Galaxy Research's running tally kept growing as more waves were identified, and different outlets reported different snapshots of it: figures as high as ~1,800 BTC (~$114-116M), with some reports of a possible fourth wave pushing the tally toward ~2,055 BTC (~$130M).
  • August 1, 2026 — Coinkite updates the official advisory with fixed firmware for every affected model.

These figures come from third-party on-chain analysis (mainly Galaxy Research), not from Coinkite — Coinkite's own advisory does not state a loss amount, and the tally kept changing in the days after the incident as more addresses were identified.

The technical cause, per Coinkite's own advisory

On Mk2/Mk3 with firmware 4.0.1 through 4.1.9 (since March 2021), the device combined its internally generated seed with the dice rolls a user entered through "Add Dice Rolls" in a way that, if fewer than 50 independent, private rolls were used, resulted in insufficient entropy.

On Mk4, Mk5 and Q with firmware before the fixed versions, affected seeds have approximately 72 bits of entropy instead of the expected 128.

Who is affected, and who isn't

Affected: seeds generated on Mk2/Mk3 firmware 4.0.1–4.1.9; Mk4/Mk5 before standard version 5.6.0 or Edge 6.6.0X; Q before standard version 1.5.0Q or Edge 6.6.0QX — unless at least 50 independent, private dice rolls were used (which on their own already provide enough entropy) or the wallet is protected by a strong, unique BIP-39 passphrase (this reduces immediate exposure but does not repair the seed — migration is still recommended).

Not affected: TAPSIGNER, OPENDIME and SATSCARD — Coinkite explicitly states these run on a different codebase and don't have this issue.

What to do now

  1. Update your Coldcard to fixed firmware: Mk2/Mk3 → 4.2.0+, Mk4/Mk5 standard → 5.6.0+, Mk4/Mk5 Edge → 6.6.0X+, Q standard → 1.5.0Q+, Q Edge → 6.6.0QX+.
  2. Do not generate a new seed before updating — older firmware is still unsafe for that step.
  3. If your seed was generated on affected firmware (and you didn't use at least 50 independent dice rolls), generate a new seed on the already-updated device.
  4. Verify the new seed's backup, its fingerprint, and a receive address directly on the device screen.
  5. Send a small test transaction before moving the rest of your funds.
  6. Only then migrate the full balance. Keep the old backup until you've confirmed everything arrived.
  7. If you used a strong, unique BIP-39 passphrase, immediate risk is lower, but Coinkite still recommends migrating.

Watch out for phishing

After an incident like this, fake messages tend to appear offering to "verify your wallet," "recover funds," or asking you to enter your seed on a website or share it with "support." Neither Coinkite nor Librería de Satoshi will ever ask for your seed, under any circumstance. Only update firmware from Coinkite's official source.

What's next

Coinkite says the investigation is ongoing and a formal technical review will follow. The theft figures circulating come from third-party on-chain analysis, mainly blockchain research firm Galaxy Research, not from an official Coinkite statement with a confirmed amount — and that tally kept being revised in the days after the incident.

If this worries you and you're not sure whether your Coldcard is affected, Librería de Satoshi offers free high-level Bitcoin custody help: group or one-on-one sessions depending on what you need, an evaluation of your risk model, and access to developers with real Bitcoin experience. No cost.

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