The Coldcard exploit explained: who lost bitcoin and who's at risk

 Coldcard-linked thefts drained bitcoin from hundreds of wallets on July 30.
 Coinkite says Mk3 seeds had about 40 bits of entropy instead of 128.
 Coldcard users must install fixed firmware and create new seeds before moving funds.
+Editor’s Note Aug. 10, 2026: Since this editorial was first published, the Coldcard exploit has logged more than 2,000 BTC in stolen funds.
 According to a deep analysis from Galaxy Research, the core theft unfolded in a tightly coordinated burst lasting about 25 minutes, while broader analysis later connected roughly 1,196 addresses and as much as 1,083 bitcoin, valued at nearly $70 million, to activity spanning approximately 41 minutes. The final figures could change as investigators continue tracing transactions on the public Bitcoin blockchain.
 A 5-Year-Old Bug Reaches Bitcoin Wallets Worldwide
 The affected wallets belonged largely to long-term holders who generated their recovery seeds using Coldcard devices running vulnerable firmware released from March 2021 onward. Coldcard is an air-gapped hardware wallet made by Canadian manufacturer Coinkite and designed to keep bitcoin (BTC) keys isolated from internet-connected devices.
 © 2026 Saint Bitts LLC Bitcoin.com. All rights reserved

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Every check is recorded, including checks that found no text change. A detected edit is therefore bounded between two checks. The publisher's exact save time is not observable from this record. Last checked 15 Aug 2026, 12:55 UTC.

1. source content difference between 9 Aug 2026, 18:47 UTC and 12 Aug 2026, 05:10 UTC source content +1 -11

   The article gained an editor's note dated August 10, 2026, stating the exploit has logged more than 2,000 BTC in stolen funds; the rotating Most Popular module also changed.

   seen 12 Aug 2026, 05:10 UTC · Captured here 14,325 chars
   What changed from the previous capture 12 lines

    Coldcard-linked thefts drained bitcoin from hundreds of wallets on July 30.
    Coinkite says Mk3 seeds had about 40 bits of entropy instead of 128.
    Coldcard users must install fixed firmware and create new seeds before moving funds.
   +Editor’s Note Aug. 10, 2026: Since this editorial was first published, the Coldcard exploit has logged more than 2,000 BTC in stolen funds.
    According to a deep analysis from Galaxy Research, the core theft unfolded in a tightly coordinated burst lasting about 25 minutes, while broader analysis later connected roughly 1,196 addresses and as much as 1,083 bitcoin, valued at nearly $70 million, to activity spanning approximately 41 minutes. The final figures could change as investigators continue tracing transactions on the public Bitcoin blockchain.
    A 5-Year-Old Bug Reaches Bitcoin Wallets Worldwide
    The affected wallets belonged largely to long-term holders who generated their recovery seeds using Coldcard devices running vulnerable firmware released from March 2021 onward. Coldcard is an air-gapped hardware wallet made by Canadian manufacturer Coinkite and designed to keep bitcoin (BTC) keys isolated from internet-connected devices.
    © 2026 Saint Bitts LLC Bitcoin.com. All rights reserved
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   FeaturedPublished:Jul 31, 2026, 8:30 PM
   The Coldcard Exploit Explained: Who Lost Bitcoin and Who's at Risk
   An attacker exploited weak seeds generated by certain Coldcard hardware wallets to steal bitcoin worth roughly tens of millions from hundreds of addresses on July 30.
   WRITTEN BY
   Jamie Redman
   SHARE
   Published: Jul 31, 2026, 8:30 PM
   Key Takeaways
   Coldcard-linked thefts drained bitcoin from hundreds of wallets on July 30.
   Coinkite says Mk3 seeds had about 40 bits of entropy instead of 128.
   Coldcard users must install fixed firmware and create new seeds before moving funds.
   Editor’s Note Aug. 10, 2026: Since this editorial was first published, the Coldcard exploit has logged more than 2,000 BTC in stolen funds.
   According to a deep analysis from Galaxy Research, the core theft unfolded in a tightly coordinated burst lasting about 25 minutes, while broader analysis later connected roughly 1,196 addresses and as much as 1,083 bitcoin, valued at nearly $70 million, to activity spanning approximately 41 minutes. The final figures could change as investigators continue tracing transactions on the public Bitcoin blockchain.
   A 5-Year-Old Bug Reaches Bitcoin Wallets Worldwide
   The affected wallets belonged largely to long-term holders who generated their recovery seeds using Coldcard devices running vulnerable firmware released from March 2021 onward. Coldcard is an air-gapped hardware wallet made by Canadian manufacturer Coinkite and designed to keep bitcoin (BTC) keys isolated from internet-connected devices.
   Many of the emptied addresses had remained dormant for years. The attacker moved rapidly, paid elevated fixed transaction fees, and left no change outputs, meaning each address was emptied completely. That pattern suggested an automated operation using a prepared list of private keys rather than customers independently moving their funds.
   The theft was not caused by phishing, malware on a user’s computer, physical device theft or a conventional remote breach. Instead, a firmware error weakened the randomness used when some Coldcard devices created wallet seeds. Those seeds looked normal but came from a far smaller range of possible combinations than users had been promised.
   Coldcard’s Random Number Generator Quietly Failed
   A Bitcoin wallet seed is a secret, commonly displayed as 12 or 24 words, from which the wallet generates its addresses and private keys. A properly generated 12-word seed contains 128 bits of entropy, a technical measure describing an enormous number of possible combinations that makes guessing the seed effectively impossible.
   Coldcard devices were supposed to obtain that randomness from a hardware random number generator inside the device’s microcontroller. The component draws from physical electrical noise that an outside observer should not be able to predict.
   During a software-library migration in 2021, however, Coinkite disclosed that two random-number functions with matching interfaces became confused. One accessed the device’s proper hardware generator. The other was a weak software fallback intended for boards without suitable hardware.
   A configuration setting disabled the default MicroPython hardware path because Coinkite supplied its own hardware wrapper. The software checked only whether that setting existed, not whether it was enabled. Because the setting was present but assigned a value of zero, the build completed successfully, while seed generation silently shifted to the weaker software generator.

   Excerpt only. The complete copy is held offline and backs quotations on this site. The original publication remains the canonical public source.

2. Earliest copy held
   seen 2 Aug 2026, 15:59 UTC · Captured here 14,393 chars
   Extracted text as captured

   Read In App
   EN
   Launch App
   News
   Market UpdatesFinanceLearning InsightsRegulation & LegalMiningBlockchainCrypto News
   LearnResearchNewsletters
   Advertise
   Advertise With UsSubmit Press ReleasePodcast Interview
   EN
   Launch App
   Finance
   Learn
   Research
   Newsletters
   Advertise
   Powered by
   FeaturedPublished:Jul 31, 2026, 8:30 PM
   The Coldcard Exploit Explained: Who Lost Bitcoin and Who's at Risk
   An attacker exploited weak seeds generated by certain Coldcard hardware wallets to steal bitcoin worth roughly tens of millions from hundreds of addresses on July 30.
   WRITTEN BY
   Jamie Redman
   SHARE
   Published: Jul 31, 2026, 8:30 PM
   Key Takeaways
   Coldcard-linked thefts drained bitcoin from hundreds of wallets on July 30.
   Coinkite says Mk3 seeds had about 40 bits of entropy instead of 128.
   Coldcard users must install fixed firmware and create new seeds before moving funds.
   According to a deep analysis from Galaxy Research, the core theft unfolded in a tightly coordinated burst lasting about 25 minutes, while broader analysis later connected roughly 1,196 addresses and as much as 1,083 bitcoin, valued at nearly $70 million, to activity spanning approximately 41 minutes. The final figures could change as investigators continue tracing transactions on the public Bitcoin blockchain.
   A 5-Year-Old Bug Reaches Bitcoin Wallets Worldwide
   The affected wallets belonged largely to long-term holders who generated their recovery seeds using Coldcard devices running vulnerable firmware released from March 2021 onward. Coldcard is an air-gapped hardware wallet made by Canadian manufacturer Coinkite and designed to keep bitcoin (BTC) keys isolated from internet-connected devices.
   Many of the emptied addresses had remained dormant for years. The attacker moved rapidly, paid elevated fixed transaction fees, and left no change outputs, meaning each address was emptied completely. That pattern suggested an automated operation using a prepared list of private keys rather than customers independently moving their funds.
   The theft was not caused by phishing, malware on a user’s computer, physical device theft or a conventional remote breach. Instead, a firmware error weakened the randomness used when some Coldcard devices created wallet seeds. Those seeds looked normal but came from a far smaller range of possible combinations than users had been promised.
   Coldcard’s Random Number Generator Quietly Failed
   A Bitcoin wallet seed is a secret, commonly displayed as 12 or 24 words, from which the wallet generates its addresses and private keys. A properly generated 12-word seed contains 128 bits of entropy, a technical measure describing an enormous number of possible combinations that makes guessing the seed effectively impossible.
   Coldcard devices were supposed to obtain that randomness from a hardware random number generator inside the device’s microcontroller. The component draws from physical electrical noise that an outside observer should not be able to predict.
   During a software-library migration in 2021, however, Coinkite disclosed that two random-number functions with matching interfaces became confused. One accessed the device’s proper hardware generator. The other was a weak software fallback intended for boards without suitable hardware.
   A configuration setting disabled the default MicroPython hardware path because Coinkite supplied its own hardware wrapper. The software checked only whether that setting existed, not whether it was enabled. Because the setting was present but assigned a value of zero, the build completed successfully, while seed generation silently shifted to the weaker software generator.
   Factory Data and Timing Replaced True Randomness
   That fallback relied heavily on predictable device information, including a chip identifier similar to a serial number and internal clock values associated with startup timing. An attacker who could narrow those inputs would face a much smaller search than the 128-bit range expected from a securely generated seed.
   Coinkite estimated the effective search space for vulnerable Mk3 seeds at about 40 bits under current assumptions. That is still a large number of possibilities, but it can be searched with specialized computing equipment, especially when an attacker can compare candidate seeds against bitcoin addresses visible on the blockchain.

   Excerpt only. The complete copy is held offline and backs quotations on this site. The original publication remains the canonical public source.