> ## Content Index > Fetch the complete content index at: https://bytevyte.com/llms.txt > Use this file to discover other available public pages before exploring further. # Coldcard RNG Bug Drains $115M; Fix Won't Save Old Seeds - URL: https://bytevyte.com/coldcard-rng-bug-drains-115m-fix-wont-save-old-seeds/ - Published: 2026-08-26T19:03:41.000Z - Updated: 2026-08-26T19:03:41.000Z - Description: A five-year-old Coldcard RNG bug let attackers drain $115M in Bitcoin. Coinkite's emergency firmware can't fix old seeds, so full migration is required. - Author: Bytevyte Editorial - Tags: quick-beats Coinkite, the Canadian maker of the Bitcoin-only **Coldcard** hardware wallet, has rushed out emergency firmware after a five-year-old **Coldcard RNG bug** let attackers drain more than $115 million in cryptocurrency from thousands of users. The first thefts were detected on July 30, 2026, and the drains continued in waves through early August. On-chain data now shows the scale of the damage. Galaxy Research's analysis puts the total at 1,789.28 BTC across 8,865 addresses. The haul was worth $114.7 million when the funds were stolen and about $138.8 million at today's prices. Other tallies count approximately 1,816 BTC from more than 5,200 addresses, putting total losses in the $116 million to $130 million range depending on the pricing snapshot. The opening sweep alone moved about 594 BTC, near $38 million, out of roughly 500 wallets in a 25-minute pass on the first night, and one victim lost C$1.6 million. The tallies are still moving. An earlier audit counted 1,596 BTC confirmed stolen from about 7,300 addresses across three attack waves, with a possible fourth wave that could push combined losses toward 2,055 BTC, close to $130 million, if victim reports are verified. ## The Coldcard RNG bug: five years in the making The root cause traces to a firmware release Coinkite shipped in March 2021, version 4.0.1\. A build configuration error made affected devices generate wallet seeds with a software pseudo-random number generator, MicroPython's Yasmarang, instead of the hardware true random number generator built into the device. The effective randomness of some seeds fell to roughly 40 bits, far below the 128 to 256 bits users expect from cold storage, so a remote attacker could brute-force the private keys without physical access. The flaw persisted through every firmware release that followed, which is why the vulnerable window stretches from March 2021 to the July 2026 patch. Coinkite published a security advisory the same day the first drains appeared, July 30, and corrected firmware followed within about 24 hours. The July 31 release fixed Mk2 and Mk3 units running firmware 4.0.1 through 4.1.9 with version 4.2.0, and a follow-up release on August 20 delivered firmware 5.6.1 for Mk4 and Mk5 devices and 1.5.1Q for the Q model. | Model | Affected firmware | Fixed firmware | | --------- | ----------------------------------- | -------------- | | Mk2 / Mk3 | 4.0.1 – 4.1.9 | 4.2.0 | | Mk4 / Mk5 | Releases before the July 2026 patch | 5.6.1 | | Q | Releases before the July 2026 patch | 1.5.1Q | The update does not behave like a routine security patch. Installing it does not repair an existing wallet. Coinkite's advisory states that any seed created on vulnerable firmware between March 2021 and the fix remains weak no matter which firmware runs on the device now, and the update protects only newly created seeds. Owners in that window must generate a completely new seed on patched hardware and transfer their coins to the new wallet. Users who supplemented their seed with independent dice-generated entropy are considered unaffected. ## What the Coldcard RNG bug means for owners The migration requirement turns a patched vulnerability into a slow-burning operational problem, and the on-chain picture shows why. Most of the stolen bitcoin has not moved since the attack. Galaxy Research's tracking shows 87.3 percent of the funds tied to the exploit, about 1,561 BTC, still sitting in wallets controlled by the attacker. Only part of the funds taken in the later waves shows signs of CoinJoin mixing and peel-chain transactions, a pattern that points to no large-scale cash-out attempt yet. Galaxy Research has shared the attacker's addresses with exchanges, compliance firms, and law enforcement to help freeze funds if they move. Alex Thorn, the firm's head of research, detailed the tracing work on X, giving affected users a way to check whether their own addresses appear in the attribution. The disclosure has added to the pressure on Coinkite. The company halted shipments of affected units after confirming the vulnerability and apologized publicly while its investigation continued. For a maker whose reputation rests on a security-first design, the Coldcard RNG bug came down to a single build flag that silently swapped a trusted hardware entropy source for a predictable software substitute. Even wallets kept air-gapped were drained, because the weakness sat in seed generation rather than in the device's network exposure. For anyone holding a Coldcard, the practical checklist is short. Confirm which firmware created the seed. If the seed dates from March 2021 onward and was generated without added dice entropy, assume it is compromised, create a fresh seed on patched firmware, and move the balance without waiting for further attacker sweeps. The attack waves that hit in early August show the sweeps were still running, and an unchecked address remains a live target. Galaxy Research's published attacker addresses offer a first check for whether a wallet has already been hit. ## Why this matters The Coldcard breach shows that hardware wallets are only as strong as the firmware that created the seed, and that self-custody carries maintenance duties most owners never expected. A single error introduced in March 2021 and undetected for five years turned thousands of cold-storage wallets into remotely guessable targets. For the roughly 8,865 addresses tied to the exploit, a full seed migration is the only safe move, and for the wider Bitcoin community the episode makes clear that verifying firmware integrity and entropy sources is part of holding keys responsibly. ## Related Articles - [Coldcard Firmware Bug: Five-Year-Old RNG Flaw Drains $130M in Bitcoin](https://bytevyte.com/coldcard-firmware-bug-five-year-old-rng-flaw-drains-130m-in-bitcoin/) ✔Human Verified --- *Researched and cross-referenced against primary sources by the Bytevyte editorial team. This article was generated with the assistance of artificial intelligence and reviewed by the Bytevyte editorial team.*