🚨 Recently, @COLDCARDwallet suffered a major private key vulnerability. Multiple waves of attacks resulted in at least 1,719 BTC (~$111M) in losses, involving over 5,200 addresses. Using Mk3 firmware 4.1.9 as an example, the SlowMist Security Team fully reproduced the attack chain and uncovered the truth behind the theft of thousands of bitcoins. 🧩 Attack flow: 1️⃣ After power-on, the remaining unpredictable state is reduced primarily to a single enumerable 32-bit pad (UID ^ SysTick), with the remaining state values either fixed or coming from very small enumerable spaces. 2️⃣ Attackers precisely model the three typical button-press consumption profiles (retail first-boot, empty-NVRAM, paper wallet) that advance the PRNG before seed generation. 3️⃣ From the weak random_bytes(32), the full deterministic pipeline (SHA-256 → BIP-39 → PBKDF2-HMAC-SHA512 → BIP-32 → address derivation) is reproduced offline. 4️⃣ GPU clusters brute-force the candidate pad space and button-count variations, then match the derived addresses against the global set of single-signature P2WPKH addresses to identify vulnerable wallets and sweep their funds. ⚙️ Root Cause: A build configuration error set MICROPY_HW_ENABLE_RNG to 0, disabling the STM32 hardware TRNG. The random number generation path silently fell back to the non-cryptographic Yasmarang software PRNG, whose state was almost entirely predictable, reducing effective entropy to ~40 bits (Mk2/Mk3) or ~72 bits (Mk4/Mk5/Q). 🔒 SlowMist Insight: Affected users should immediately upgrade to the patched firmware, generate a completely new seed, transfer a small amount of funds as a test, confirm the new address works correctly, then migrate all remaining funds. Full analysis 👉https://medium.com/@slowmist/coldcard-111-million-theft-a-deep-dive-into-the-private-key-vulnerability-8e51d1a969d3(SlowMist)