Full Report
An attacker drained 1,196 Bitcoin addresses in 41 minutes on July 30, taking 1,082.65 BTC worth about $70.2 million at the time. Galaxy Research mapped the sweep and tied it to a firmware flaw in Coldcard, the Bitcoin-only hardware wallet made by Canadian firm Coinkite. A March 2021 firmware integration error routed seed generation to a deterministic software pseudorandom number generator (PRNG
Analysis Summary
# Incident Report: Coldcard Hardware Wallet PRNG Flaw Exploitation
## Executive Summary
An attacker exploited a long-standing firmware flaw in Coinkite’s Coldcard hardware wallets to drain 1,082.65 BTC (approx. $70.2 million) from 1,196 addresses in a 41-minute window. The vulnerability stemmed from a 2021 integration error that caused wallets to generate predictable seeds using a software-based fallback pseudorandom number generator (PRNG) instead of a hardware-based source of entropy. While Coinkite released emergency firmware updates, affected users must manually migrate to new seeds to remediate the risk.
## Incident Details
- **Discovery Date:** July 30, 2026 (via blockchain analysis)
- **Incident Date:** July 30, 2026
- **Affected Organization:** Users of Coinkite Coldcard Hardware Wallets
- **Sector:** Cryptocurrency / Financial Technology
- **Geography:** Global (Firm based in Canada)
## Timeline of Events
### Initial Access
- **Date/Time:** July 30, 2026 (Sweep occurred over 41 minutes)
- **Vector:** Exploitation of a predictable software PRNG (Yasmarang)
- **Details:** The attacker identified addresses generated using a specific vulnerable firmware version and used brute-force/offline seed reconstruction to gain control of the private keys.
### Lateral Movement
- **N/A:** This was a cryptographic exploit; the attacker did not move through a traditional network but instead "moved" across the blockchain to sweep various independent addresses linked by the same vulnerability.
### Data Exfiltration/Impact
- **Assets Stolen:** 1,082.65 BTC (approximately $70.2 million USD).
- **Scope:** 1,196 unique Bitcoin addresses were drained.
### Detection & Response
- **Discovery:** Galaxy Research mapped the sweep by identifying a specific signature (30 sat/vB fee, no-change signature) across the transactions.
- **Response Actions:** Coinkite released emergency firmware updates on July 31, 2026, for all affected models (Mk2, Mk3, Mk4, Mk5, and Q).
## Attack Methodology
- **Initial Access:** Cryptographic weakness; bypass of hardware entropy.
- **Persistence:** Not applicable (one-time theft).
- **Privilege Escalation:** Not applicable.
- **Defense Evasion:** Use of a specific transaction signature that mimicked legitimate owner "sweeps" to move coins.
- **Credential Access:** Offline brute-forcing of candidate seeds by constraining variables (UID, timer state, and RNG history).
- **Discovery:** Mapping vulnerable addresses via public blockchain data.
- **Impact:** Financial theft via unauthorized transaction signing.
## Impact Assessment
- **Financial:** $70.2 million USD in stolen Bitcoin.
- **Data Breach:** Compromise of private keys (seeds) for 1,196 users.
- **Operational:** Emergency firmware deployment and requirement for users to manually migrate funds.
- **Reputational:** Significant scrutiny regarding Coinkite’s firmware testing and PRNG integration logic.
## Indicators of Compromise
- **Behavioral indicators:** Transactions with a specific 30 sat/vB fee and "no-change" signature occurring in rapid succession on July 30.
- **Vulnerability:** Firmware versions Mk3 (4.0.1–4.1.9), Mk4/Mk5 (pre-5.6.0), and Q (pre-1.5.0Q).
## Response Actions
- **Containment:** Coinkite released patched firmware (e.g., v4.2.0 for Mk3, v5.6.0 for Mk4/Mk5) that correctly enables the hardware RNG.
- **Eradication/Recovery:** Users advised to generate entirely new seeds on patched firmware and transfer remaining assets. Note: Patching the firmware *does not* secure a seed generated under the old version.
## Lessons Learned
- **Integration Risks:** Third-party libraries (like MicroPython) may have fallback behaviors (like Yasmarang) that activate silently if specific macros are not defined exactly as the library expects.
- **Entropy Verification:** Hardware wallets must strictly validate that entropy is sourced from a high-quality hardware RNG and not a deterministic software fallback.
- **Migration Necessity:** In cryptographic failures, a software patch is often insufficient for security; the underlying secret (the seed) is permanently compromised and must be replaced.
## Recommendations
- **User Action:** Immediately update Coldcard firmware and migrate funds to a newly generated seed if the original seed was created on a vulnerable version without sufficient manual dice rolls.
- **Development Best Practices:** Implement rigorous automated testing to verify the source of entropy during the seed generation process.
- **Security Architecture:** Utilize "Dice Rolls" (user-provided entropy) for seed generation to mitigate the impact of firmware-level RNG failures.
- **Defense-in-Depth:** Implement multisig configurations using devices from different manufacturers to ensure a single firmware flaw cannot result in a total loss of funds.