BleepingComputer

Fireship

Hacker News

The whole point of a hardware wallet is that your keys never touch the internet. Coldcard just proved that’s not enough if the firmware is generating predictable keys in the first place.
Here’s what happened: Coldcard’s MicroPython-based firmware had two random number generators sharing the same function name. A flag meant to disable the weak built-in RNG was set to zero instead of being left undefined, so an <code>if not defined</code> check passed incorrectly and the weak RNG ran instead of the secure hardware one. On bare metal with no OS, MicroPython’s fallback RNG pulled from deterministic inputs: the chip serial number and a timer. Attackers looped through every possible serial/timer combination, derived private keys offline, matched them to on-chain addresses, and drained wallets. No physical access required. No seed phrase sharing. Just math.
The numbers vary by source — somewhere between $88M and $130M stolen, 4,500 to 7,000 wallets hit, at least a dozen separate attacker groups involved. The bug dates to 2021. Affected firmware covers Mk2/Mk3 versions 4.0.1 through 4.1.9 and several Mk4, Mk5, and Q versions before recent patches.
Victims who caught it in time faced a second problem: trying to rescue funds meant racing attackers in the mempool, where higher fees let attackers front-run the transactions. The only workaround was submitting rescue transactions directly to mining pools to skip the public mempool entirely.
Coinkite has pushed firmware updates, but here’s the part that stings: updating firmware doesn’t fix already-generated seeds. If your seed was created on vulnerable firmware, it’s compromised. You need a new seed and you need to move your funds. The one exception: seeds generated with at least 50 dice rolls aren’t considered at risk from this specific flaw.
The fallout is spreading. Bitcoin developers froze the BIP-110 soft fork. Kraken’s CSO is calling for audits across the hardware wallet industry. The broader market reaction is muted — BTC down about 1% — but the reputational damage to the hardware wallet category is harder to price. People buy these devices specifically because they’re supposed to be immune to remote attacks. That assumption just took a direct hit.

Trends

A critical firmware vulnerability in COLDCARD hardware wallets (Mk2 through Q versions, dating back to 2021) caused devices to silently fall back to Yasmarang, a deterministic software RNG, instead of the STM32 hardware RNG. Because deterministic RNGs are predictable, attackers could reconstruct wallet seeds offline and drain funds without physical access. Estimated losses range from $88.6 million to over $130 million across thousands of addresses, exploited by at least a dozen hacker groups. Victims who followed all best practices — air-gapped devices, never exposing seed phrases — were still affected. Firmware patches are available, but they do not fix already-generated seeds; users must generate new seeds on patched firmware and migrate funds. Seeds supplemented with 50+ dice rolls are considered safe from this specific flaw.

COLDCARD's RNG flaw let attackers drain wallets that never touched the internet