$38 Million in Bitcoin Vanishes After Coldcard Key Vulnerability – Maker Suspects AI-Assisted Attack
Coinkite, the company behind the popular Coldcard hardware wallet, is facing a major security crisis after a critical flaw in older devices appears to have allowed attackers to drain roughly 594 BTC-about $38 million-from users’ wallets.
The most alarming twist: Coinkite believes the attacker may have used artificial intelligence to comb through its open-source firmware and uncover a subtle weakness that even the company’s own AI-assisted review failed to detect just weeks earlier.
What Happened to Coldcard Users
The issue affects Coldcard’s Mk3 model running firmware versions released after 4.0.1. According to the company’s advisory, seeds generated on those devices were significantly more predictable than they should have been.
In practice, that means the mnemonic seed phrases-the core secret that secures a user’s Bitcoin-did not have the level of randomness required for strong cryptographic security. An attacker with enough insight into the vulnerability could narrow down the possible seeds to a manageable set and then systematically guess them, ultimately taking control of affected wallets.
Coldcard’s newer models-Mk4, Q, and Mk5-are not believed to be impacted based on the company’s initial analysis. The flaw appears limited to the Mk3 line under certain firmware versions, but the financial damage from that narrow window is already severe.
How the Vulnerability Was Exploited
The vulnerability was actively exploited early Friday, when large volumes of Bitcoin began moving out of addresses associated with Coldcard users. Blockchain analysts estimate that at least 594 BTC were siphoned off in a coordinated series of transactions.
Because the security failure lies in the seed generation process itself, the attacker did not need physical access to the devices. Instead, they only needed to:
– Understand how the flawed firmware generated seeds
– Use that knowledge to compute or filter down possible seeds
– Derive the corresponding private keys
– Sweep funds from affected addresses as quickly as possible
The attack appears to have been highly automated and carefully timed, suggesting substantial preparation and technical sophistication.
Why Coinkite Thinks AI Was Involved
Coinkite’s firmware is open source, meaning anyone can inspect the code, download old versions, and study how every step of the wallet’s logic works. That openness is usually considered a security benefit, because bugs can be spotted by the broader community.
This incident, however, highlights the double-edged nature of transparency in the age of AI.
Coinkite revealed that it had already run its own AI-based analysis on earlier versions of the firmware weeks before the theft-but that internal review did not surface the vulnerability. When the incident unfolded and the bug became apparent, the company concluded that the attacker likely used a more targeted AI-driven approach to analyze historical firmware changes and hunt specifically for weaknesses in key and seed generation.
The suspected workflow for such an attacker might have looked like this:
– Feed multiple older firmware versions into an AI model
– Ask the model to highlight changes affecting randomness, entropy, or seed derivation
– Probe those sections of code more deeply, simulating how predictable outputs might be
– Develop an exploit strategy based on reduced entropy or flawed randomness
If this theory is correct, it marks a new stage in crypto security, where adversaries use AI not just for phishing or social engineering, but as a tool to reverse-engineer and break wallet internals at scale.
What Owners of Coldcard Mk3 Wallets Need to Do
For owners of the Mk3 model, especially those who generated their seed after firmware version 4.0.1, the situation is urgent. The company has effectively said: if your seed was created on an affected Mk3 device, you must assume your funds could be at risk.
The recommended steps are:
1. Stop using the at-risk seed immediately
Do not continue adding funds to any wallet derived from a potentially compromised seed.
2. Migrate to a secure wallet and a fresh seed
– Use a device and firmware version that is confirmed not to be affected (such as Mk4, Q, or Mk5, according to early analysis).
– Generate a completely new seed, ideally in a secure offline environment.
3. Transfer all funds to the new wallet
Move your Bitcoin and any other supported assets from addresses tied to the old seed into addresses derived from the new, securely generated seed.
4. Verify firmware authenticity
Make sure your device firmware is genuine and up to date, using only officially distributed binaries and recommended verification methods.
5. Preserve your old data for investigation
While you should not use the old seed again, it may be worth keeping the device and any logs or notes you have. This information could help security researchers or aid in any potential legal or law-enforcement response.
Why Seed Randomness Matters So Much
The entire security model of a hardware wallet rests on one core principle: the secret keys must be impossible to guess. That depends on strong entropy-true randomness-when generating the seed.
If a bug inadvertently reduces this randomness, the search space that an attacker must cover shrinks from astronomically large to something a sophisticated adversary can brute-force or narrow down with intelligent heuristics.
In this case, the firmware flaw appears to have weakened that entropy in a way that was not obvious at a glance, but catastrophic once understood and exploited. This is why even a small oversight in the seed-generation path can erase all the other sophisticated security protections a wallet offers.
Open Source, AI, and a New Threat Landscape
This incident underscores a tension that has quietly been building in software security:
– Open source makes it easier for defenders to audit code.
– Open source plus AI also makes it dramatically easier for attackers to scan huge codebases and historical revisions for exploitable mistakes.
Tools that can ingest thousands of lines of code, track how functions change across versions, and reason about complex flows are now widely accessible. While security teams are starting to use such tools to detect flaws proactively, this case suggests attackers may already be one step ahead in creatively applying them.
For crypto hardware in particular, that means:
– Every change to random number generation, seed derivation, or signing logic is a high-risk area that must be scrutinized.
– Historical firmware versions-often ignored after an update-can become a treasure map when analyzed with modern AI.
– “Security by obscurity” is no longer an option, and “security by transparency” now requires much more aggressive, automated review tools on the defender’s side.
Lessons for Hardware Wallet Users
For individual users, this event doesn’t mean hardware wallets are obsolete-but it does highlight how to use them safely:
– Treat seed generation as the most critical moment. If there’s any doubt about the firmware or the device, generate a new seed later on a known-good device.
– Keep firmware updated, but cautiously. Updates fix vulnerabilities, but can also introduce new ones. Wait for early security feedback when possible, especially for major changes.
– Avoid long-term dependence on a single device generation. As products age, so does their security posture. Rotating into newer hardware-after it has been battle-tested-can reduce risk.
– Use layered defenses. For large holdings, consider multisignature setups, splitting control across multiple devices or vendors so a single firmware bug cannot empty your entire balance.
How the Industry Is Likely to Respond
The Coldcard incident will almost certainly push the wider wallet ecosystem to rethink its development and audit practices. Likely responses include:
– Deeper, AI-assisted security audits before releases, especially for cryptographic components and randomness functions.
– Independent, third-party cryptographic reviews of seed and key-generation mechanisms, with formal proofs where possible.
– More aggressive bug bounties targeting firmware, encouraging ethical hackers to find vulnerabilities before criminals do.
– Better communication protocols for quickly warning users when a critical issue is discovered, minimizing window-of-exploit time.
It may also accelerate movement toward designs where even a partially predictable seed cannot easily be exploited-for example, by requiring multiple independent entropy sources, including user-generated randomness, or by distributing signing authority across multiple devices.
A Wake-Up Call for AI in Security
Perhaps the most far-reaching implication is the role AI now appears to play in offensive security. What used to require teams of skilled reverse engineers over months can potentially be done faster and at lower cost by combining human expertise with powerful code-understanding models.
Defenders will have to assume that every line of their public code is being continuously analyzed by adversaries with tools capable of:
– Identifying non-obvious correlations in randomness or state
– Spotting unsafe refactors across historical versions
– Simulating attack strategies based on subtle flaws in logic
In that world, “we ran a manual audit” is no longer enough. Just as attackers are turning to AI, wallet makers and other critical-infrastructure developers must do the same-systematically and repeatedly.
What This Means for Bitcoin Holders Going Forward
For Bitcoin holders, the news is unsettling, but it offers a clear set of takeaways:
– Self-custody remains powerful-but it is not “set and forget.” Devices, firmware, and operational practices must evolve as threats do.
– Rely on vendors that treat open-source security seriously, are transparent about incidents, and respond quickly when issues arise.
– Regularly reassess how and where your keys are stored, especially if you hold significant sums or rely on older hardware.
The Coldcard Mk3 flaw and the suspected AI-assisted exploit are likely to be studied in detail for years as a pivotal moment in the intersection of crypto, hardware, and artificial intelligence. For now, affected users need to act quickly to protect remaining funds-and the entire ecosystem must adapt to a world where human and machine attackers are working together to find the smallest crack in the strongest vault.