Blockchain security firm SlowMist has published a postmortem on the Qubic Wallet. Its finding is uncomfortable: some private keys could be recovered from as few as six network observations.
The analysis, released on October 20, 2026, follows an October 18 breach. In that breach, approximately 2.94 trillion QU, valued at around $1.3 million, was drained from 1,404 wallets within hours.
A random number generator that wasn’t random enough
The root problem sits in how the wallet created seeds. Seeds are the master secrets that generate account private keys.
According to SlowMist, Qubic Wallet built these seeds with JavaScript’s Math.random() function. Each seed was a 55-character string of lowercase letters.
On paper, the seed format looks very strong. SlowMist noted the theoretical seed space is 26^55, a number so large that guessing a seed by brute force should be hopeless.
In practice, the weak PRNG state undermined that math. SlowMist found that an attacker effectively faced about 2^32 possibilities, which is small enough to brute-force.
The leak in the headers
SlowMist reported that outputs from the same random stream were exposed in plaintext through a field called dejaVu. That field sits inside the wallet’s protocol request headers.
Anyone watching network traffic could collect those values. With as few as six observations, SlowMist said, the PRNG state could be worked out and private keys potentially recovered.
The vulnerability did not hit every user equally. It mainly affected weak-entropy environments, places where the browser or app supplied poorer randomness.
SlowMist specifically pointed to Safari on Mac before October 18, 2026, and the Qubic iOS app before July 2025. The research summary also flagged iOS and iPadOS devices more broadly as the higher-risk group.
SlowMist was also clear that the issue lived in the wallet implementation. It was not attributed to flaws in the core Qubic protocol itself.
Halting the chain and freezing the funds
Once the theft was identified on October 18, Qubic halted its network at tick 85,371,949.
Validators were able to freeze about 87.1% of the stolen funds on-chain. The remaining 12.9% was frozen by the MEXC exchange.
The same day, Qubic shipped a fix in web wallet version 4.26.4. The patch swaps Math.random() for crypto.getRandomValues(), the browser’s cryptographically secure randomness function.
The update separates the generation of new account seeds from the random stream exposed in the headers. However, header generation itself was left unchanged. So new seeds no longer draw from the leaky source. The dejaVu values, meanwhile, keep coming from the old process.
Not Qubic’s first security scare this year
The October breach follows a smaller security event in July 2026 connected to Qubic’s GitHub.
What this means for Qubic users and wallet builders
The weak-entropy windows SlowMist identified are tied to specific platforms and dates. Users who generated seeds in those environments sit in a different risk category than everyone else.
The 4.26.4 patch addresses how new account seeds are created. A patch cannot retroactively strengthen a seed that already exists. That makes the timing and platform of seed creation the key detail for anyone reviewing their own exposure.
For wallet developers on any chain, the takeaway is concrete. A seed space of 26^55 means nothing if the generator behind it collapses to about 2^32 possibilities.
Disclosure: This article was edited by John Chen. For more information on how we create and review content, see our Editorial Policy.