The safest way to store Bitcoin was just hacked...

Video thumbnail: The safest way to store Bitcoin was just hacked...
Aug 5, 20265m 10s video lengthFireship

The Signal

Coldcard, an airgapped Bitcoin wallet marketed as a high-security standard, was compromised when a firmware error caused it to use a weak, deterministic number generator instead of its custom secure one. This allowed attackers to derive seed phrases without physical access or phishing, resulting in the theft of nearly 1,800 Bitcoin from over 7,000 wallets since July 30, 2026.

The Case

  • The vulnerability stemmed from a faulty flag check in the firmware, which forced the system to rely on a basic MicroPython generator that used only chip serial numbers and timers to 'randomize' inputs.1:55
  • Because these inputs were deterministic and enumerable, attackers were able to brute-force the keys of thousands of users who had previously assumed their assets were secured by high-entropy, offline generation.2:45
  • Victims attempting to save their funds faced a secondary threat: attackers monitored the public mempool for rescue transactions, then broadcasted their own competing transactions with higher fees to steal the remaining coins before they could reach a new, secure wallet.3:30
  • The only viable rescue path was to bypass the public mempool entirely by sending funds directly to a mining pool, a workaround that relied on centralized coordination to outmaneuver the exploit.
  • CoinKite, the Canadian manufacturer of the device, has acknowledged the flaw and halted shipments of all remaining warehouse inventory, which was confirmed to contain the same broken firmware.4:05

Developer Demo

  • In a separate segment, the narrator demonstrated using Lovable—an AI development platform—to build a predictions market, noting that the tool successfully managed payments and a Postgres database despite hitting a policy-related bug that required reverting to 'plan mode' to resolve.

The 1 Minute Signal Take

The hack serves as a stark reminder that even 'airgapped' hardware is only as secure as its implementation logic. Users who hold funds on compromised hardware should prioritize secure migration via direct-to-miner submission, as the race conditions inherent in the public mempool leave standard rescue attempts dangerously exposed.

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Why It Matters

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Written by: 1 Minute Signal Editorial Team