Coldcard Firmware Flaw Exposes Bitcoin Wallet Seeds

Coinkite disclosed a Coldcard firmware flaw on July 30 that could generate Bitcoin wallet seeds with insufficient entropy, and researchers linked three waves of thefts totaling 1,367 BTC (about $88.6 million) across 4,585 addresses to wallets created by affected devices, according to BleepingComputer. Coinkite released emergency fixes, but public evidence does not prove who exploited the weakness or that AI identified it. Users must generate a new seed with patched firmware and move funds, as updating firmware alone cannot repair an already exposed seed.

Coldcard Firmware Flaw Exposes Bitcoin Wallet Seeds Researchers linked three waves of Bitcoin thefts totaling 1,367 BTC, about $88.6 million across 4,585 addresses, to a Coldcard firmware entropy flaw disclosed July 30. Coinkite confirmed that affected firmware could generate seeds from a weak software fallback and issued fixes, but public evidence does not prove who exploited the weakness or that AI identified it. A flaw in Coldcard hardware-wallet firmware could generate recovery seeds with far less randomness than intended. Coinkite disclosed the defect on July 30 and released emergency fixes. Separately, researchers linked three waves of Bitcoin thefts totaling 1,367 BTC , worth about $88.6 million , across 4,585 addresses to wallets created by affected devices, according to figures reported by BleepingComputer. The public evidence supports a likely link, not a proven account of who carried out the thefts or how the flaw was discovered. How seed generation failed Coldcard firmware was intended to obtain entropy from the device's hardware random-number generator. Coinkite's technical account says an integration error instead allowed MicroPython's deterministic Yasmarang generator to supply values in an affected path. Because a recovery seed determines a wallet's private keys, sufficiently predictable seed generation can let an attacker test candidates offline and compare derived addresses with the public blockchain. Coinkite estimated roughly 40 bits of effective entropy for affected Mk2 and Mk3 devices and about 72 bits for newer models. Block's independent engineering analysis reached a stricter result: for Mk2 and Mk3 firmware in the affected version range, it found no cryptographic entropy beyond reconstructable state, while newer devices exposed at most 2^32 securely distinguished output streams in the analyzed path. The estimates use different threat models, so they should not be treated as interchangeable measurements. What the theft data shows BleepingComputer reported that Galaxy Research identified three theft waves. The first swept about 1,083 BTC from 1,196 addresses in 41 minutes on July 30. Later waves brought the tracked total to 1,367 BTC across 4,585 addresses. On-chain patterns can link transactions and wallet characteristics, but they do not by themselves prove that every affected address was generated by the flaw or that all waves came from one operator. The incident did not break Bitcoin's cryptography and did not require remote access to the hardware wallet. The failure occurred earlier, when long-lived wallet secrets were created from inadequate entropy. Updating firmware is not enough Coinkite published fixed firmware across affected product lines. A firmware update prevents the vulnerable generation path from being used again, but it cannot strengthen a seed that was already created. Coinkite's guidance is to install patched firmware, generate a new seed, and move funds to addresses derived from that new seed. Importing the old seed into another wallet preserves the exposure. Claims that AI found or accelerated exploitation remain unverified. Coinkite said it assumed AI assistance, but neither its advisory nor Block's technical analysis established that an attacker used AI. The demonstrated engineering lesson is narrower: security-critical products need tests that verify the active entropy source, including fallback paths and build-time configuration, rather than merely confirming that a hardware RNG exists. Key Points - 1Coinkite confirmed that affected firmware could generate wallet seeds through a weak deterministic fallback and released emergency fixes. - 2Researchers linked 1,367 BTC in thefts across 4,585 addresses to affected Coldcard-generated wallets, but the public evidence does not establish one operator or exact exploit method. - 3Users must generate a new seed with patched firmware and move funds; updating firmware alone cannot repair an already exposed seed. Scoring Rationale The confirmed seed-generation flaw affects long-lived cryptographic secrets and has been linked, with appropriate uncertainty, to thefts totaling roughly $88.6 million. The incident has direct engineering relevance for entropy integration, firmware testing, and wallet remediation. Sources Primary source and supporting public references used for this report. Practice with real FinTech & Trading data 90 SQL & Python problems · 15 industry datasets Active Verified Users by Income TierEasy /problems/sql/active-verified-users-by-income Technology Stocks with High BetaMedium /problems/sql/technology-stocks-with-high-beta Portfolio Performance ScorecardHard /problems/sql/portfolio-performance-scorecard 250 free problems · No credit card See all FinTech & Trading problems /problems/datasets/fintech