tl;dr
The ESP32 chip, commonly used in affordable Bitcoin hardware wallets, has a critical vulnerability (CVE-2025-27840) due to insufficient entropy in its random number generator. This flaw compromises the chip's ability to create secure private keys, exposing users to risks such as malicious firmware u...
The ESP32 chip, widely used in affordable Bitcoin hardware wallets, has a critical vulnerability identified as CVE-2025-27840. This flaw arises from insufficient entropy in its random number generator, severely compromising the security of private keys and exposing users to risks such as malicious firmware updates and brute-force attacks.
Unlike high-end wallets like Ledger, Trezor, or Coldcard, which incorporate dedicated hardware security modules (HSM) designed to generate secure entropy and safely store cryptographic secrets, the ESP32 lacks these essential features. This absence makes the chip particularly vulnerable to attacks, as its weak randomness can allow attackers to predict or compute private keys.
Moreover, the chip’s design flaw potentially enables unauthorized firmware updates that could silently sign transactions without user consent, heightening the risk to user funds. This vulnerability predominantly affects low-cost, open-source wallet solutions that utilize the ESP32, while premium wallets remain unaffected due to their robust security architectures.
Developers leveraging the ESP32 for wallet construction are strongly advised to integrate additional external entropy sources or consider migrating to more secure chip models to bolster security. Meanwhile, users relying on ESP32-based wallets should stay vigilant for updates and, where feasible, transfer their Bitcoin holdings to more secure devices until patches or redesigned hardware become available.
Overall, the ESP32’s popularity is driven by its affordability and versatility, making it a common choice for DIY and experimental wallets. However, this convenience comes with significant security trade-offs that must be addressed to protect users in the evolving cryptocurrency landscape.