Summary
On 30–31 July 2026, Coinkite published a security advisory disclosing that a firmware build error caused ColdCard seed generation to silently fall back to a software RNG (MicroPython) instead of the STM32 hardware RNG. On the Mk3 this reduced generated-seed entropy to roughly ~40 bits (vs. the intended 128) — brute-forceable on commodity hardware. Approximately 594 BTC (~$38M) was drained from ~500 wallets on 31 July 2026 (Coinkite's investigation into that sweep is ongoing).
Affected, per Coinkite:
- Mk2 / Mk3: firmware 4.0.1 – 4.1.9 (fixed in v4.2.0+; device-generated seeds)
- Mk4 / Mk5 / Q: reduced to ~72 bits before fixed firmware (standard v5.6.0 / Edge v6.6.0X; Q v1.5.0Q / Edge v6.6.0QX)
- Seeds created with ≥50 user dice rolls, or protected by a strong BIP-39 passphrase, are not affected in the same way.
- Fix: update firmware, generate a new seed, and migrate funds.
Advisory: https://blog.coinkite.com/coldcard-mk3-seed-generation-warning/
Why this concerns Caravan
Caravan documents and supports ColdCard as a first-class signing device — and explicitly lists the affected Mk3:
apps/coordinator/README.md — lists "Coldcard Mk2, Mk3, & Mk4"- Driver:
packages/caravan-wallets/src/coldcard.ts
- UI:
apps/coordinator/src/components/Coldcard/ (ColdcardSigner.jsx, ColdcardFileReader.jsx, …)
Caravan does not generate the ColdCard seed (the device does), so this is not a flaw in Caravan's code. But because Caravan names Mk2/Mk3 directly as supported devices, users who set up ColdCard for a Caravan multisig may hold funds on affected seeds and would reasonably look to Caravan for guidance.
Suggested changes
- Add a visible warning next to the ColdCard entries in the README and in the ColdCard signer UI, linking Coinkite's advisory and the fixed-firmware / reseed guidance.
- Deprioritize / de-emphasize the affected Mk2/Mk3 models in the supported-device list until a user is known to be on fixed firmware with a freshly generated seed.
Happy to open a PR for the docs/UI change if that's welcome.
Disclosure note
This references a public third-party (Coinkite) advisory, not an undisclosed vulnerability in Caravan, so I'm filing publicly on the issue tracker. Happy to route via SECURITY.md if you'd prefer.
Sources
Summary
On 30–31 July 2026, Coinkite published a security advisory disclosing that a firmware build error caused ColdCard seed generation to silently fall back to a software RNG (MicroPython) instead of the STM32 hardware RNG. On the Mk3 this reduced generated-seed entropy to roughly ~40 bits (vs. the intended 128) — brute-forceable on commodity hardware. Approximately 594 BTC (~$38M) was drained from ~500 wallets on 31 July 2026 (Coinkite's investigation into that sweep is ongoing).
Affected, per Coinkite:
Advisory: https://blog.coinkite.com/coldcard-mk3-seed-generation-warning/
Why this concerns Caravan
Caravan documents and supports ColdCard as a first-class signing device — and explicitly lists the affected Mk3:
apps/coordinator/README.md— lists "Coldcard Mk2, Mk3, & Mk4"packages/caravan-wallets/src/coldcard.tsapps/coordinator/src/components/Coldcard/(ColdcardSigner.jsx,ColdcardFileReader.jsx, …)Caravan does not generate the ColdCard seed (the device does), so this is not a flaw in Caravan's code. But because Caravan names Mk2/Mk3 directly as supported devices, users who set up ColdCard for a Caravan multisig may hold funds on affected seeds and would reasonably look to Caravan for guidance.
Suggested changes
Happy to open a PR for the docs/UI change if that's welcome.
Disclosure note
This references a public third-party (Coinkite) advisory, not an undisclosed vulnerability in Caravan, so I'm filing publicly on the issue tracker. Happy to route via SECURITY.md if you'd prefer.
Sources