Image Credit: Shutterstock
Galaxy Research estimates that at least 15 different attackers have exploited the Coldcard wallet vulnerability as new victim reports expose previously unidentified transaction clusters.
High-confidence losses have reached 1,596 BTC across three major attack waves and 14 smaller incidents, affecting roughly 7,300 addresses. A suspected fourth wave could increase the total to about 2,055 BTC, worth approximately $130 million.
One Victim Report Exposed a 12 BTC Theft Across 126 Addresses
Galaxy Head of Research Alex Thorn said direct victim reports have helped investigators connect additional attacks to recovery seeds generated with vulnerable Coldcard firmware. One report involving a loss of less than 1 BTC led researchers to another cluster that removed 12 BTC from 126 addresses. Galaxy classified the transactions as a separate attacker footprint.
The cluster may not have been linked to the wider incident without confirmation that one affected address belonged to a wallet created with a vulnerable Coldcard seed.
Unlike an exchange breach with a known group of compromised addresses, the Coldcard incident involves independently controlled wallets. Researchers must combine victim reports with onc-hain transaction structures to identify related thefts.
Galaxy said 73 victims have contacted the firm for assistance. It continues to share information with affected users and provide relevant address data to law enforcement agencies, exchanges, and blockchain investigation companies.
Three Major Waves and 14 Smaller Attacks Stole 1,596 BTC
Galaxy’s confirmed total covers three major attack waves and 14 smaller attacker footprints. The opening sweep on July 30 removed 1,082.65 BTC from 1,196 addresses in 41 minutes.
Galaxy said each major wave appeared internally consistent with one operator. Researchers have not determined whether those operators were connected or whether additional attackers began exploiting the vulnerability after it became public.
The suspected fourth wave remains outside the confirmed total because Galaxy lacks enough direct victim reports linking every address to vulnerable Coldcard-generated seeds.
Mk2 and Mk3 Seeds Contained About 40 Bits of Entropy
The vulnerability caused impacted firmware to use a deterministic software random-number fallback instead of the intended hardware generator during seed creation.
Coinkite estimates that some Mk2 and Mk3 seeds contained about 40 bits of effective entropy instead of the expected 128 bits. That reduced search space allowed attackers to generate possible seeds offline and check their derived addresses for Bitcoin balances.
Fixed firmware is available, but an update cannot repair an existing weak seed. Affected users must generate a new recovery phrase on patched firmware and move their Bitcoin to fresh addresses.
