#What happened with Coldcard hardware wallets and Bitcoin security?
Coldcard hardware wallets were once seen as a strong solution for keeping your cryptocurrency secure by storing private keys offline. However, recent findings have revealed a serious vulnerability that enabled attackers to siphon off significant amounts of Bitcoin, estimated between $100 million and $111 million, affecting thousands of wallets. A suspected later wave of attacks added approximately 389 BTC to the total.
Alex Thorn, from the on-chain analysis team at Galaxy Digital, confirmed these alarming findings through thorough forensics. The vulnerability was especially concerning because victims had adhered to all recommended security measures. They did not fall for phishing scams, there was no key leakage, and no user errors were involved. The problem lay within the firmware itself.
#How did the vulnerability occur in Coldcard firmware?
The issue originates from firmware version 4.0.1 released on March 17, 2021, which introduced a serious bug affecting the random number generator. This flaw led to wallet seeds being generated with significantly less entropy, or randomness, than necessary. Some seeds offered as little as 40 bits of entropy. A properly secured Bitcoin wallet would use a much higher amount of entropy, making the wallet almost impossible to guess. Unfortunately, this vulnerability did not go unnoticed and allowed attackers to use open-source brute-force tools to reconstruct these weak seeds and access affected wallets.
The flaw went undetected for over five years, illustrating the potential longevity of security issues. Coinkite only disclosed the vulnerability on July 30, 2026, and a patched version was released immediately afterward. Patching the firmware, though, does not recover lost funds or correct seeds previously generated under the faulty system. Affected users must create entirely new seeds on the updated firmware and transfer their assets to newly generated addresses.
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#What do the theft patterns indicate?
Galaxy Digital's analysis of the thefts uncovered at least 15 distinct attackers correlated with three confirmed waves of theft, impacting around 7,300 addresses. As of early August, the confirmed stolen Bitcoin had increased to 1,719 BTC, with some estimates suggesting total potential losses could exceed $130 million when accounting for additional suspicious activity.
One surprising element observed in the analysis is that most of the stolen Bitcoin remains unspent on-chain. While attackers moved the assets, they did not follow typical money laundering patterns by converting or dispersing their haul.
The pattern of theft waves indicates a degree of organization, suggesting these attackers were aware of the vulnerability before it was made public.
#What should Coldcard users do?
Given that Coldcard has established itself as one of the most security-focused hardware wallets, many of its users are technically savvy individuals who understand the importance of self-custody. The unfortunate reality is that those most dedicated to managing their own keys have been compromised by a significant flaw in the tool trusted to secure those keys.
For anyone currently using a Coldcard device with firmware from version 4.0.1 onward, acting quickly is critical. Users must update their firmware immediately and migrate any funds to freshly generated seeds. Procrastination could result in additional risk; as the identification of a potential fourth wave of attacks indicates that the window for exploitation remains open for addresses that have not yet been exploited. Prompt action is essential to safeguard assets in light of these troubling developments.