Coinkite CEO Links Coldcard Flaw to 1,816 BTC in User Losses

Coinkite CEO Rodolfo Novak said a flaw in Coldcard firmware caused roughly 1,816 Bitcoin (BTC) in losses — about $116 million at the time — across more than 5,200 addresses, with affected users now forced to generate entirely new seed phrases.

The vulnerability affects Coldcard firmware version 4.1 and later and can bypass the device's hardware random-number generator, Novak said. He dated the losses to a window between July 30 and Aug. 4. That timing matters: any seed phrase generated on a vulnerable device during that period, or before on affected firmware, cannot be trusted.

The operational consequence is blunt. A firmware update can fix the flaw on new devices, Novak said, but it cannot repair seed phrases already created. The patch does not alter phrases already in use — it only closes the door for future generations. Every user who created a seed on a compromised device must move funds to a freshly generated phrase on patched hardware.

How was the flaw found?

Novak's account of the discovery has drawn pushback from the Bitcoin development community. He said a new AI model found the flaw after at least 15 prior reviews had failed to catch it.

Bitcoin developers disputed that framing. James O'Beirne, a Bitcoin developer, said he privately raised concerns about Coldcard's random-number generation in May 2025 — months before the flaw was publicly acknowledged. If accurate, that timeline suggests the issue was on someone's radar well before an AI system flagged it, and it complicates the narrative that machine analysis outperformed 15 rounds of human review.

The dispute is more than reputational. Coldcard's value proposition rests on its security model, and a compromised random-number generator sits at the foundation of that model. A hardware wallet's seed phrase is only as strong as the entropy that produced it.

Why random-number generation is the weak point

The flaw's mechanics explain the severity. When a hardware random-number generator can be bypassed, the resulting seed phrase may derive from predictable or insufficient entropy. Predictable seeds mean an attacker can, in principle, reconstruct private keys without ever touching the device. That is why the damage cannot be patched retroactively — the weak phrases already exist on the blockchain, and no firmware release can retroactively strengthen them.

For the affected cohort, the recovery path is narrow: generate a new seed phrase on updated firmware and sweep funds from the old wallet before anyone else does. That is the operational reality Novak left users with, regardless of how the discovery story resolves.

The episode also raises questions about vendor disclosure practice. O'Beirne's May 2025 warning, communicated privately, did not surface publicly until after the losses occurred. Whether Coinkite acted on that warning, and on what timeline, will likely shape how the hardware-wallet community weighs Coldcard's engineering claims going forward.

For now, the immediate deadline is user-side: anyone who generated a seed phrase on Coldcard firmware 4.1 or later should verify their exposure and migrate funds to a new seed on patched devices — before the next wave of sweeps targets the more than 5,200 addresses already hit.