Key Takeaways
- • Galaxy Digital researchers identified approximately $70 million in Bitcoin stolen from Coldcard wallet users due to a firmware vulnerability that compromised seed phrase randomness generation.
- • The attack occurred rapidly across six blocks in 41 minutes, with the vast majority of funds drained in less than one hour, affecting 1,196 addresses in the initial identified sweep.
- • Coinkite, the Canadian manufacturer of Coldcard, acknowledged full accountability for the firmware bug and released emergency patches (version 4.2.0+ for Mk3, 5.6.0+ for Mk4/Mk5, 1.5.0Q+ for Coldcard Q).
- • The theft targeted individual self-custody holders rather than institutional or exchange holdings, with loss distribution dominated by addresses holding 1-50 BTC in aggregate value, despite sub-1 BTC addresses comprising the majority by count.
- • Firmware updates alone cannot secure existing compromised seeds; users must generate entirely new recovery phrases on patched firmware and migrate their Bitcoin to restore security.
Summary
Researchers at Galaxy Digital have documented a significant security breach affecting Coldcard hardware wallets, with approximately $70 million in Bitcoin stolen through exploitation of a firmware vulnerability. The exploit centered on a bug in Coldcard's seed phrase generation process that dramatically reduced the randomness of how the wallet creates its secret recovery phrase—the cryptographic foundation for wallet security.
The attack unfolded with notable speed and precision. According to Galaxy Digital's analysis, the theft occurred across six blockchain blocks spanning 41 minutes, with the majority of funds drained in less than one hour. The researchers identified 1,196 affected addresses in the initial attack wave, suggesting the transactions were broadcast in batches rather than continuously streamed across the network. The loss profile indicates individual self-custody holders were primarily targeted rather than institutional investors or exchange holdings, with the value concentration skewed toward addresses containing 1-50 BTC each despite a greater numerical prevalence of smaller sub-1 BTC accounts.
Coinkite, the Canadian manufacturer behind Coldcard, has taken responsibility for the vulnerability and released emergency firmware updates across its product line. Affected users should update to version 4.2.0 or later for Mk3 models, 5.6.0 or later for Mk4 and Mk5 models, and 1.5.0Q or later for Coldcard Q devices. These patches remove the vulnerable software fallback path and enforce the device's intended hardware-based true random number generator for seed creation. However, Coinkite emphasized a critical limitation: firmware updates alone cannot secure wallets that were already compromised. Users with potentially affected devices must generate entirely new recovery phrases on the fixed firmware and actively migrate their Bitcoin holdings to newly generated addresses to restore security.
The incident highlights a critical tension in self-custody security architecture. Coldcard's design as an offline "cold storage" device was intended to provide maximum security against remote attacks by keeping private keys isolated from internet-connected systems. The firmware vulnerability bypassed this fundamental security model by introducing weakness at the entropy generation layer—the earliest stage of wallet creation. Galaxy Digital's findings that the attack was "identifiable onchain" suggest forensic analysis may help identify affected addresses, though recovery prospects for stolen funds remain limited absent voluntary actor cooperation or law enforcement intervention.
The attack unfolded with notable speed and precision. According to Galaxy Digital's analysis, the theft occurred across six blockchain blocks spanning 41 minutes, with the majority of funds drained in less than one hour. The researchers identified 1,196 affected addresses in the initial attack wave, suggesting the transactions were broadcast in batches rather than continuously streamed across the network. The loss profile indicates individual self-custody holders were primarily targeted rather than institutional investors or exchange holdings, with the value concentration skewed toward addresses containing 1-50 BTC each despite a greater numerical prevalence of smaller sub-1 BTC accounts.
Coinkite, the Canadian manufacturer behind Coldcard, has taken responsibility for the vulnerability and released emergency firmware updates across its product line. Affected users should update to version 4.2.0 or later for Mk3 models, 5.6.0 or later for Mk4 and Mk5 models, and 1.5.0Q or later for Coldcard Q devices. These patches remove the vulnerable software fallback path and enforce the device's intended hardware-based true random number generator for seed creation. However, Coinkite emphasized a critical limitation: firmware updates alone cannot secure wallets that were already compromised. Users with potentially affected devices must generate entirely new recovery phrases on the fixed firmware and actively migrate their Bitcoin holdings to newly generated addresses to restore security.
The incident highlights a critical tension in self-custody security architecture. Coldcard's design as an offline "cold storage" device was intended to provide maximum security against remote attacks by keeping private keys isolated from internet-connected systems. The firmware vulnerability bypassed this fundamental security model by introducing weakness at the entropy generation layer—the earliest stage of wallet creation. Galaxy Digital's findings that the attack was "identifiable onchain" suggest forensic analysis may help identify affected addresses, though recovery prospects for stolen funds remain limited absent voluntary actor cooperation or law enforcement intervention.
Go deeper than the headline
Research every firm in this story, track the ones that matter and get the daily briefing — free for 7 days.