Coldcard Incident Exposes Hardware Wallet Security Flaws: A Critical Look at Ledger, Trezor, and Coldcard

Hardware wallets have long been considered secure storage solutions for cryptocurrencies. However, recent incidents highlight the importance of evaluating their security models beyond certification and hardware specifications.

The Coldcard incident in 2026 is a prime example. A firmware update replaced the hardware random number generator (RNG) with a software implementation, reducing entropy to 40 bits. This led to the theft of over 38 million dollars in Bitcoin and severe reputational damage for the device's manufacturer.

This incident refutes the premise that certification of a Secure Element is enough to classify a device as resistant to attacks. A more comprehensive evaluation of hardware wallets must consider verifiable attack vectors, including physical extraction, fault injection, supply chain compromise, and secret generation.

Three prominent manufacturers, Ledger, Trezor, and Coldcard, respond differently to these vectors.

Ledger relies on a certified Secure Element (SE) with Common Criteria certification. However, its proprietary firmware limits the ability for users to verify the complete binary code. This opacity is seen as an acceptable cost by some, but others consider it a trust risk not mitigated by certification.

Trezor's model has evolved from a general-purpose microcontroller architecture toward a scheme with a Secure Element. The company's Safe 7 series employs a dual-chip architecture, distributing responsibilities between two chips from different vendors. This reduces the attack surface and complicates an isolated vulnerability.

Coldcard was designed for advanced Bitcoin users and operates in air-gapped mode, signing transactions via MicroSD or QR code without connecting to a networked computer. However, its recent entropy failure demonstrates that even a device with dual Secure Elements can lose all advantage if the process prior to key writing produces predictable material.

Comparison of these models highlights the importance of considering threat models rather than brands. For remote adversaries without physical access, all three devices offer equivalent guarantees in transaction signing and key isolation.