A critical flaw in COLDCARD hardware wallet firmware, involving a faulty Random Number Generator (RNG), has likely enabled the theft of $88.6 million in Bitcoin.

Key Takeaways

  • An RNG flaw in COLDCARD firmware led to an estimated $88.6 million Bitcoin theft.
  • Attackers used automated tools to drain over 4,500 addresses.
  • Firmware updates fix future seed generation but do NOT secure existing compromised seeds.
  • Affected devices include various versions of Mk2, Mk3, Mk4, Mk5, and Q series.

Researchers have identified a devastating vulnerability in COLDCARD hardware wallet firmware that is suspected to be the root cause behind the theft of approximately $88.6 million in Bitcoin. The breach targeted thousands of wallets whose recovery seeds were generated using a flawed Random Number Generator (RNG).

The Mechanics of the Attack

According to Galaxy Research, the attack unfolded in waves, with the first major wave draining 1,083 BTC ($70.2 million) in just 41 minutes. The sophistication of the attack was evident in its execution; every transaction used an identical, hardcoded fee rate of 30 satoshis per virtual byte—significantly higher than the market median. This pattern strongly suggests the use of an automated exploitation tool rather than manual transfers by owners.

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Why This Matters

BozokMedia analysis shows that this incident highlights a critical single point of failure in hardware security: the randomness of seed generation. When a device fails to use its dedicated hardware RNG and falls back to a deterministic software generator, the 'unpredictable' private keys become mathematically reconstructible. This allows attackers to pre-calculate potential seeds and match them against addresses seen on the blockchain.

'A flaw in the RNG doesn't just weaken security; it effectively hands the keys to the kingdom to anyone capable of running the right script.'

Technical Root Cause

The security teams at Block discovered that an integration error caused the COLDCARD firmware to bypass the STM32 hardware RNG. Instead, it utilized a deterministic MicroPython fallback that relied on predictable system timing and microcontroller identifiers. This lack of cryptographic entropy made the resulting wallet seeds vulnerable to offline brute-force attacks.

Did You Know?: High-value attackers often study the blockchain for weeks to identify targets before launching a coordinated strike, as seen in this $88M heist.

Frequently Asked Questions

Is updating my firmware enough to secure my funds?

No. Updating the firmware only ensures that new seeds are generated securely. If your current seed was generated on an affected version, you must move your funds to a new wallet.

Which devices are affected?

Affected devices include Mk2 and Mk3 (firmware 4.0.1–4.1.9), Mk4 and Mk5 (pre-5.6.0), and Q devices (pre-1.5.0Q).