A suspected fourth wave of attacks against Coldcard-generated Bitcoin wallets moved approximately 448.7 BTC from 709 potential victim addresses, according to Alex Thorn, head of firmwide research at Galaxy Research. The latest activity shows the wallet-draining campaign remained active days after the underlying entropy flaw became public.
The updated figure is higher than the initial estimate of roughly 389 BTC. Combined with three earlier waves, observed losses have reached about 1,816 BTC from more than 5,200 addresses since July 30, making the incident one of the largest hardware-wallet-related theft campaigns recorded on-chain.
🚨 LIKELY 4TH ORGANIZED WAVE COLDCARD ATTACK OCCURRING RIGHT NOW
THERE ARE STILL SIMILAR TXS IN THE MEMPOOL WAITING TO BE CONFIRMED AND THE PREVIOUSLY-CONFIRMED TXS SIGNAL RBF OPT-IN, CHECK YOUR FUNDS AND YOU MAY BE ABLE TO RBF YOUR WAY OUT OF THIS
pattern identified:
blocks…— Alex Thorn (@intangiblecoins) August 3, 2026
On-Chain Pattern Points to Another Coordinated Sweep
Thorn identified transaction activity occurring at roughly 13.8 sweeps per Bitcoin block, about 45 times the rate measured during a pre-incident control period. That acceleration supports the assessment that the transfers represent coordinated exploitation rather than ordinary wallet activity.
Most of the suspected victim funds moved to newly created destination addresses rather than a small group of common collection wallets. Some proceeds later reached second-hop addresses, indicating a more fragmented transaction pattern that complicates attribution and fund monitoring.
Thorn described the affected addresses as likely Coldcard victims because their unspent transaction outputs matched the characteristics of wallets exposed to the previously identified firmware weakness. He nevertheless noted that the conclusion relied on pattern analysis rather than direct confirmation from every holder, making the fourth-wave classification highly probable but not yet independently proven for each address.
The transactions also used Bitcoin’s Replace-by-Fee function. While transfers remained unconfirmed in the mempool, affected users could potentially broadcast conflicting transactions with higher fees and move their funds first, creating a narrow emergency window in which victims might outrun the attacker.
The incident should not be interpreted as attackers extracting private keys from otherwise secure devices in real time. Coinkite confirmed that affected firmware generated some wallet seeds with insufficient entropy, allowing attackers to reproduce candidate seeds offline and derive the same private keys without possessing or connecting to the original hardware.
Weak Seed Generation Changes the Custody Risk Model
On affected Mk2 and Mk3 firmware, Coinkite estimated that the effective search space could have fallen to approximately 40 bits. Later Mk4, Mk5 and Q devices received additional entropy but could still fall near 72 bits under affected firmware, leaving some device-generated seeds substantially weaker than the intended 128-bit security level.
Coinkite has released corrected firmware for all affected product lines. However, installing an update does not strengthen an existing seed, so holders must generate a completely new seed under fixed firmware and transfer assets to verified addresses, making key migration the only durable remediation for exposed wallets.
The repeated sweeps expose a testing weakness that extends beyond one manufacturer. Security reviews had confirmed that Coldcard’s intended hardware random-number generator existed in the firmware, but they did not verify that the wallet-creation process actually called it, showing the danger of auditing cryptographic components without testing their complete execution path.
The episode changes the scope of hardware-wallet due diligence. Procurement controls should cover device provenance and firmware history, but firms must also verify entropy architecture, seed-generation procedures and independent testing, because offline storage cannot protect funds whose private keys were predictable from creation.
Multisignature custody provides an additional defense when keys are generated independently on different devices or implementations. None of the first three identified waves appeared to affect multisignature wallets, reinforcing the value of removing any single vendor or seed generator as a complete point of failure.
Governance teams should preserve device inventories, firmware records, wallet fingerprints and migration evidence while activating incident-reporting procedures where client or regulated assets may be exposed. Transaction-monitoring systems should also flag coordinated consolidations and unusual spending from dormant addresses, making forensic readiness essential for rapid attribution and stakeholder disclosure.
The fourth wave remains an evolving on-chain event, and the final loss estimate may change as pending transactions confirm or users successfully replace them. For holders, however, the operational conclusion is already clear: any wallet created with affected firmware must be treated as compromised until its funds are moved to a newly generated seed.
