Coldcard Entropy Flaw Exposes Nearly $90M in Bitcoin

Key Point

Coldcard generated some seeds through MicroPython’s Yasmarang software PRNG instead of the hardware entropy source. On some models, the effective entropy collapsed to around 40 bits. The flaw shipped in March 2021 and stayed in publicly readable firmware for more than five years. Galaxy Research’s tally reached 4,585 addresses and nearly $90 million after attackers swept 500 addresses. Coinkite’s working assumption is that someone used AI to comb the publicly available firmware for the bug.

Why it matters: Weak seed generation can turn self-custody into a direct loss channel because private-key knowledge may transfer Bitcoin control immediately.

Market Sentiment

Bearish, Stress-on, Tech-driven, Fear.

Reason: Attackers swept 4,585 addresses and nearly $90 million through a Coldcard seed-generation flaw, which points to direct custody risk.

Similar Past Cases

In 2023, the Milk Sad vulnerability in Libbitcoin Explorer exposed wallets generated by the bx seed command because vulnerable versions used a weak Mersenne Twister PRNG for cryptographic key material. Attackers used the flaw to steal large amounts of funds on 12 July 2023, and Libbitcoin Explorer 3.8.0 later removed the problematic entropy generation command. (Milk Sad) The key difference is that Milk Sad centered on a command-line wallet tool, while the current event centers on a hardware signer.

Ripple Effect

Weak entropy can spread risk through any wallet workflow that depends on one device as the only source of seed safety. If users and vendors cannot clearly separate affected seeds from safe seeds, then custody trust could shift toward independently verifiable key generation. If more swept addresses appear, then the incident could reinforce demand for reproducible builds and smaller trusted cores.

Opportunities & Risks

Opportunities: If Coinkite or researchers publish clear affected-device and firmware guidance, then migrating funds to independently generated seeds can reduce exposure for affected users.

Risks: If additional addresses are swept or the affected keyspace remains searchable, then reducing reliance on single-device seed generation limits repeat compromise risk.