How a $116 Million Bitcoin Sweep Exposed a Deadly Hardware-Wallet Flaw

Coldcard, not Bitcoin, Was the Failure Point

This was not a Bitcoin protocol break. It was an entropy failure in one hardware wallet brand. Galaxy Research traced four waves of thefts affecting more than 5,200 individual addresses, with attackers moving approximately 1,816 Bitcoin worth nearly $116 million. The earlier nearly $89 million estimate flagged the incident; the later figure reflects Galaxy's broader read on potentially affected funds.

The mechanism matters. Block's security team said the fault was a firmware integration error that routed seed generation to a deterministic software pseudorandom number generator instead of proper hardware randomness. In practical terms, some recovery outputs became narrow enough that attackers could reproduce candidates offline and test them against public blockchain data without touching the device. That makes this a wallet-security incident, not a verdict on Bitcoin itself.

For investors, that distinction matters. The attack surface is the vendor's key generation, not the Bitcoin network. The main risk is therefore trust in affected wallets and the possibility that more drained funds begin moving. For now, though, the market has treated the event as a contained operational shock.

How a July 30 Sweep Revealed the Vulnerability

The clearest signal came earlier this month. On July 30, attackers hit 1,196 Bitcoin addresses in 41 minutes, taking 1,082.65 BTC worth roughly $70.2 million at the time. That speed suggests a narrowed search space that could be tested in bulk offline, rather than attackers hunting random cold wallets one by one.

What actually broke

The problem dates to a March 2021 firmware integration error. Instead of using the STM32 hardware RNG, seed generation was routed to a deterministic software pseudorandom number generator. In plain English, the process relied on repeatable inputs instead of fresh hardware entropy.

That matters because Bitcoin wallets are only as strong as their randomness. A normal 12-word BIP-39 seed carries 128 bits of entropy. Coinkite estimates the vulnerable Coldcard output was down to roughly 40 bits on the Mk3 and about 72 bits on later models. Even without exaggerating the outcome, that gap is enough to make the flaw serious.

What the patch fixes - and what it does not

Coinkite shipped emergency firmware on July 31, but that does not repair seeds created under the vulnerable code. Installing the update does not fix an existing seed, and restoring the old seed on patched firmware or another wallet can carry the weakness forward.

There is also an important limit to how far the evidence should be taken. No public report has reconstructed a victim's seed and matched it to a drained address. So this is proof that a specific firmware path produced weaker-than-intended keys and that at least one major sweep exploited that weakness. It is not public proof of every compromised device in the wild.

What Markets and Users Are Doing With the News

The market response has been relatively contained. Since the first major theft wave on July 30, Bitcoin and Ethereum prices each fell less than 1%. That suggests traders have so far treated the incident as wallet-specific rather than a problem with Bitcoin itself.

That framing will hold only if users act quickly. Coinkite has already told users to move their funds, and the urgent firmware was released the next day. If affected holders create fresh seeds on patched firmware and move coins now, the overhang from stolen BTC is less likely to hit exchanges all at once.

The bear case does not require a protocol failure. It only requires slow remediation, new on-chain telltales, or fresh attention on the roughly $116 million already moved. If users delay or restore old seeds onto new devices, the weakness travels with them and the story can shift from a vendor-specific scare to a broader crypto-risk headline.

What to watch next

• Whether affected users follow guidance to generate new seeds on patched firmware
• Whether exchange inflows stay contained rather than becoming the main absorption zone for moved funds
• Whether Bitcoin and Ethereum continue to treat the incident as noise
• Whether similar July 30-style sweeps reappear