Morning Edition · Monday, August 3, 2026Published at 1:28 AM EDT · New York

Coldcard Wallet Flaw From 2021 Lets Attacker Drain $89 Million in Bitcoin Without Touching a Device

Galaxy Research traces the theft to seeds built from predictable software randomness, and the roughly 1,367 stolen bitcoin remain unspent across the attacker's addresses.

Save

Coldcard Wallet Flaw From 2021 Lets Attacker Drain $89 Million in Bitcoin Without Touching a Device

The attack required no access to any physical device, which makes it a notable example of how self-custody can fail. According to Galaxy Research, relayed by CoinDesk, a March 2021 firmware integration error in Coldcard hardware wallets routed seed generation to a deterministic software pseudorandom number generator (PRNG) rather than the device's STM32 hardware random-number generator (RNG). The result was private keys built from far less randomness (less entropy) than their owners believed.

The root cause is a cryptographic implementation defect, not a smart-contract or exchange failure. Because the flawed randomness depended on a constrained set of inputs (the device identifier, timer state, and prior RNG-call history), an attacker who can reconstruct those conditions can regenerate candidate seeds offline, derive their addresses, and check them against the public ledger. No recovery phrase, computer, or physical access is required. Every coin taken so far was held in an address created after the vulnerable firmware shipped on March 17, 2021.

The losses have grown across successive waves. crypto.news reports that a fourth suspected wave moved 448.7 BTC from 709 addresses, with some transactions still potentially replaceable. Alex Thorn of Galaxy Research warned publicly that the newest wave was underway and urged owners of affected devices to move their funds immediately. In total the sweeps have reached roughly 1,367 BTC, close to $89 million at bitcoin's level near $63,000, across 4,585 addresses.

Two details stand out. First, the stolen bitcoin remains unspent, which is unusual for a theft of this scale. That is consistent either with an operator waiting for scrutiny to fade or with one who lacks a way to launder so visible a sum. Second, as CoinDesk noted separately, smaller holders are now moving coins back onto exchanges for safety, the reverse of the shift into self-custody that followed the 2022 FTX collapse.

Veracity: Corroborated

87/100

If true, who benefits: Institutional custodians and exchange-traded products absorbing balances from spooked self-custody holders, Coinkite's hardware-wallet competitors, and the still-anonymous attacker.
The nuance: Multiple independent outlets confirm the 2021 software-RNG flaw and the roughly 1,367 BTC swept, but the loss figure grew across waves ($38M to $70M to $89M) and the coins staying unspent leaves the operator's identity and motive unproven.

An open-source-intelligence read of how likely this story is true with its real nuance, not a judgment of any outlet. It assesses the claim, weighing independent and adversarial reporting. How we label confidence.

What this means

The exposed party is the self-custody hardware model itself. Coldcard's claim, like that of every certified signing device, is that a coin generated on a device kept offline (air-gapped) is safe from remote theft. A biased-randomness flaw breaks that guarantee for keys already created, with no attack on the smart-contract or network layer. The immediate beneficiaries are custodians and exchange-traded products, which take in balances from holders who conclude that managing their own randomness is beyond them. The losers are the open-source self-custody vendors whose trust premium rested on the assumption that certified hardware protects keys.

What to watch

Whether the roughly 1,367 unspent BTC begin to move, which would signal that the attacker has found a laundering path and force exchanges to screen tainted deposits.
Whether other hardware-wallet vendors disclose similar entropy or firmware-integration audits, since a shared library or design pattern would widen the affected population well beyond Coldcard.
Net flows of small-balance bitcoin onto exchanges, a measure of how far this incident pushes risk-averse holders away from personal key management.

Observations to monitor, not financial advice.

3 sources

Synthesized from: CoinDesk · crypto.news · Polylog editors

Part of a tracked trend

Implementation Bugs, Not Just Exploits, Threaten Custody

Cryptographic implementation errors in wallets and signers (biased nonces, reused randomness, faulty derivation) keep surfacing as a distinct custody risk alongside smart-contract exploits, eroding the assumption that certified hardware protects keys.