COLDCARD Seed Generation Flaw Linked to Nearly $89 Million Bitcoin Theft
COLDCARD firmware flaw in seed generation linked to $88.6M Bitcoin theft across 1,367 BTC.
A firmware error in COLDCARD hardware wallets (Mk2, Mk3, Mk4, Mk5, Q models) weakened seed generation by routing to a deterministic software fallback instead of the hardware RNG, resulting in seeds with only 40–72 bits of entropy instead of 128. Galaxy Research linked three suspected Bitcoin thefts totaling 1,367.05 BTC (~$88.6M) across 4,585 addresses to exploitation of this flaw. Coinkite's firmware updates cannot repair seeds already generated; affected users must create entirely new seeds and migrate their funds.
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The lesson from this incident
Full lessonA firmware bug in COLDCARD hardware wallets caused seed generation to fall back to a deterministic software routine instead of the hardware random number generator (RNG), reducing cryptographic entropy from a secure 128 bits down to just 40–72 bits. This weakness made wallet seeds computationally feasible to brute-force, allowing attackers to drain approximately 1,367 BTC across thousands of affected addresses. The critical distinction here is that unlike a software patch, the damage is irreversible — firmware updates cannot retroactively strengthen already-generated seeds, meaning affected users must migrate funds to entirely new wallets. This incident underscores that cryptographic key material is only as strong as the entropy source used to generate it, and hardware security devices must be rigorously validated for their core randomness functions.
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Indicators of Compromise
Extracted by AI from the linked source. Not reviewed by an editor. How this works
- malware — COLDCARD seed generation flaw (CVE pending)