A 2021 firmware migration routed COLDCARD seed generation through a deterministic MicroPython RNG instead of the STM32 hardware RNG. Attackers enumerated candidate seeds offline and drained ~1,367 BTC (~$88.6M) from ~4,585 addresses beginning July 30, 2026; updating firmware does not repair an already-generated seed.
On July 30, 2026, Galaxy Research identified waves draining ~1,367 BTC (~$88.6M) from ~4,585 addresses, traced to a COLDCARD firmware RNG flaw. A 2021 firmware migration routed seed generation through ngu.random.bytes(), which fell back to MicroPython's deterministic Yasmarang generator instead of the STM32 hardware RNG because a build guard tested whether a macro existed rather than whether it was enabled. Seeds generated on Mk2/Mk3 v4.0.0-v4.1.9 had no secure reseed (recoverable in ~2^40 trials) and Mk4/Q/Mk5 devices retained only a 32-bit reseed (~2^72). Attackers enumerated candidate seeds offline and matched them against public wallet data. Block's Bitcoin Engineering and Security teams root-caused the flaw and disclosed it to Coinkite. Fixed releases are Mk2/Mk3 v4.2.0, Mk4/Mk5 v5.6.0, Q v1.5.0Q and the corresponding Edge versions; updating firmware does not repair an already-generated seed.
Attackers enumerated candidate seeds offline and matched them against public wallet data, then drained ~1,367 BTC from ~4,585 addresses in waves beginning July 30, 2026. Updating firmware does not repair an already-generated seed.