Affected Systems
COLDCARD hardware wallets: Mk2/Mk3 firmware 4.0.1-4.1.9, Mk4/Mk5 before 5.6.0 (standard) or 6.6.0X (Edge), Q devices before 1.5.0Q (standard) or 6.6.0QX (Edge). Seeds generated using the flawed RNG are compromised. TAPSIGNER, OPENDIME, and SATSCARD products not affected.
Exploitation Status
Active exploitation confirmed. Attackers stole 1,367 BTC ($88.6M) from 4,585 addresses across three waves starting July 30, 2026, approximately 30 hours before public disclosure. Automated tooling used; attackers had pre-identified high-value targets.
Business Impact
Critical impact for organizations and individuals holding Bitcoin in affected COLDCARD wallets. The RNG integration error caused firmware to use a deterministic software fallback (MicroPython Yasmarang) instead of the STM32 hardware RNG. Attackers can reconstruct wallet seeds offline using observable microcontroller identifiers and timing values, then derive private keys to steal funds. Firmware updates do not repair previously generated seeds. Organizations must assume all seeds created on vulnerable firmware versions are compromised and initiate immediate fund migration.
Urgency
🔴 Immediate
Recommended Actions
- Immediately identify all COLDCARD devices running vulnerable firmware: Mk2/Mk3 versions 4.0.1-4.1.9, Mk4/Mk5 before 5.6.0/6.6.0X, Q before 1.5.0Q/6.6.0QX
- Update to patched firmware: version 4.2.0+ (Mk2/Mk3), 5.6.0+ (Mk4/Mk5 standard), 1.5.0Q+ (Q standard), or 6.6.0X/6.6.0QX (Edge releases)
- Generate new wallet seeds on patched firmware and verify the new wallet address directly on the device display
- Migrate all funds from old wallets: send a small test transaction first, then transfer remaining Bitcoin to the new wallet address
- Retain old seed backups until migration is confirmed complete, then securely destroy compromised seed material