Qubic halts its chain after weak wallet seeds let an attacker drain 1,404 wallets

Qubic’s validators stopped the network after an attacker emptied 1,404 wallets in under two hours. Between 23:42 UTC on 17 October and 01:26 UTC on 18 October 2026, about 2.94 trillion QU, worth roughly $1.3 million to $1.4 million depending on the outlet, left wallets whose recovery seeds turned out to be guessable. The chain was halted at tick 85,371,949, according to Qubic’s post on X, published at 12:29 UTC on 18 October and relayed by Cointelegraph, Bitcoin.com News, CryptoTicker and Crypto Adventure.

The Qubic wallet hack did not break the protocol. It went through the software that writes a new wallet’s secret. Qubic’s open-source web wallet picked the 55 letters of each seed with JavaScript’s Math.random(), a function built for games and animations, not for secrets. A fix replacing it with the browser’s cryptographic generator was written at 03:28 UTC on 18 October, about two hours after the last stolen transfer, and merged into the wallet’s GitHub repository 28 minutes later.

Most of the loot has not gone far. In Qubic’s words, quoted by Cointelegraph, 87.1% of the drained funds “never left the Qubic network and remain frozen in place”, while the remaining 12.9% reached MEXC, which froze the receiving account. What happens to those funds now depends on a vote of the Computors, the operators who run Qubic. No date has been given as of 19 October.

From 23:42 UTC to tick 85,371,949: how the drain unfolded

The unauthorised transfers started at 23:42 UTC on Saturday 17 October and stopped at 01:26 UTC on Sunday 18 October, a window of about 1 hour 44 minutes, according to Bitcoin.com News, CryptoTicker and Crypto Adventure. In that time the attacker swept 1,404 wallets. Qubic’s own records, cited by Crypto Adventure, show 2,939,606,531,944 QU moving into seven collecting addresses. None of the coverage published those addresses.

The Computors then halted the chain at tick 85,371,949. Qubic counts its progress in ticks rather than blocks. The exact UTC time of the halt has not been published; CryptoTicker places it during the night of 18 October. An update from Coinotag said the network was still stopped at 03:27 UTC on 19 October. While it is halted, no transfer and no smart contract call goes through.

Qubic’s developers also said they moved other balances that were at risk to safety before the attacker could reach them, according to Bitcoin.com News and CryptoTicker. How many wallets and how much value that covered has not been disclosed.

Exchanges reacted on their side. MEXC froze the account that received part of the stolen QU within about an hour, Cointelegraph reported, and then paused QUBIC deposits and withdrawals at the project’s request, according to Finwire and The Crypto Times. Bitget suspended QUBIC deposits and withdrawals from 18 October; Bitcoin.com News described the suspension as maintenance without tying it to the theft, while CryptoTicker linked the two. XT did the same on 18 October for QUBIC and KASPLEX, citing wallet upgrades and maintenance, Finwire reported.

The token took a hit. Bitcoin.com News reported QUBIC down more than 10% at 10 am Eastern time (14:00 UTC) on Sunday 18 October. CryptoTicker put the stolen amount at about 2% of the token’s market value. One QU trades at a tiny fraction of a cent, which is why a theft counted in trillions of tokens comes to about $1.3 million.

Where the 2.94 trillion QU are now

The halt froze most of the stolen funds where they sat. Of the total, 87.1%, about 2.56 trillion QU, is still on the Qubic network, according to Qubic figures reported by Cointelegraph and CryptoMeter. The other 12.9%, about 379.26 billion QU, went to MEXC and is locked in the account the exchange froze.

Freezing the chain is what kept the 87.1% from reaching other exchanges or mixers. It also means that every other Qubic user is stuck too, since nobody can move anything until the network restarts. Whether MEXC will hand back its 12.9% is not known.

The bug: a 55-letter seed picked with Math.random()

A Qubic seed is a string of 55 lowercase letters. On paper that is enormous: 26 to the power of 55 possible strings. In practice, a seed is only as hard to guess as the process that picked its letters, and the code shows where that process was weak.

Before the fix, two screens of the qubic/wallet web app, the one that creates a new vault and the one that edits a seed, each held a small seedGen() function. It looped 55 times and took a letter with Math.floor(Math.random() * 26). Math.random() is a pseudo-random generator: its output follows from a small internal state, and browsers do not promise it is unpredictable. An attacker who can narrow down that state can rebuild the seeds it produced, derive the matching addresses and check which ones hold funds. investingLive described the function as not designed for cryptographic secrets.

Nobody has published how this attacker narrowed the candidates. Cointelegraph reported the same code change but found no confirmation of the root cause beyond Qubic’s own statement that the flaw was fixed, and Qubic has promised a full technical report only after a recovery plan is in place.

What wallet 4.26.4 changed

The commit, titled “fix: use cryptographically secure seed generation”, was written by the developer behind the GitHub account J0ET0M and merged at 03:56 UTC as pull request #294. A release bot published v4.26.4 at 04:22 UTC on 18 October. Both screens now call a shared generateSeed() function. It draws random bytes from crypto.getRandomValues, the browser’s Web Crypto source, which is designed for keys and secrets.

It also removes a subtler bias. A byte has 256 values and the alphabet 26 letters, so mapping bytes to letters with a simple remainder would favour some letters. The new code throws away bytes of 234 and above. Its comment reads: “234 is the largest multiple of 26 below 256. Reject the remaining byte values so modulo does not favor some letters over others.” If Web Crypto is missing, the function refuses to produce a seed at all instead of falling back to a weaker source. A test file checks those cases.

The patch protects seeds created from now on. It does nothing for seeds already made with the old code: a seed does not change when the app is updated.

Qubic wallet hack: how to tell if your seed is exposed

Qubic lists three environments as exposed, according to Cointelegraph, CryptoTicker and Crypto Adventure, which relayed the project’s statement:

• Seeds created in any browser on an iPhone or iPad before 18 October 2026.
• Seeds created in Safari on a Mac before 18 October 2026.
• Seeds created in the Qubic iOS app before July 2025.

What counts is where and when the seed was first generated, not where you use the wallet today. A seed made in Safari on a Mac in 2024 and later imported into another device carries the same weakness. Qubic also warned that wallets created in those environments may be at risk even if they were not among the 1,404 drained, per Crypto Adventure.

Qubic has not explained why it names Apple browsers and not others. The code published on GitHub shows the same Math.random() routine was used by the web wallet whatever the browser. That does not prove seeds made in Chrome or Firefox were equally guessable, since the project has not said so, but it is a fact worth knowing for anyone who generated a seed in Qubic’s web wallet before version 4.26.4. Whether third-party wallets copied the same seed code is not known; no other wallet has been named.

Practical steps follow from what Qubic has said so far:

• Find out where and when your seed was created. If it matches one of the three cases above, treat it as compromised.
• Nothing can be moved while the chain is halted. When it restarts, Qubic says it will give instructions to create a new wallet with a securely generated seed and move funds there.
• Create any new seed with wallet 4.26.4 or later, or with a hardware wallet, never with an older copy of the web app.
• Ignore anyone who contacts you offering to recover funds, and never type or send your seed to anyone. Qubic says it will never write to users first, ask for a seed or charge a recovery fee, according to The Crypto Times.
• If you lost funds, Qubic asks victims to file a police report, according to CryptoTicker. In France, that means a complaint with the police or gendarmerie.

QEARN, Qubic’s staking feature, was reported unaffected, although like everything else it is paused by the halt.

Why the seed generator is the soft spot of a hot wallet

A seed phrase is the single secret behind a wallet: whoever knows it controls the funds, on any device, without touching the blockchain’s rules. That is why an attack like this one needs no exploit of the chain at all. The attacker only has to guess seeds, compute the addresses and look for balances.

Most advice on seeds is about storage: never photograph them, never keep them in the cloud, write them on paper or metal. Our guide to seed phrase security covers that part. The Qubic case is about the step before storage. If the program that draws the seed uses a predictable source, the best backup in the world protects a secret someone else can rebuild.

This risk sits mostly with software that generates keys on an internet-connected device, the hot wallets that run in a browser or a phone app. Secure code takes randomness from the operating system or from the browser’s Web Crypto interface. Users cannot check this themselves, which leaves open-source code, audits and a project’s track record as the signals available. Hardware wallets generate seeds on a dedicated chip, though they are not immune either, as the Coldcard case below shows.

A chain that a quorum can stop

Bitcoin cannot be paused by anyone. Qubic can, because it is run by a fixed set of Computors that agree on each tick. In this case that design kept most of the stolen QU in place and gives the operators a chance to decide on restitution.

The same power raises questions holders should weigh. A group able to freeze the network and vote on what happens to specific balances can also make mistakes or come under pressure. The core team says it is identifying affected wallets and preparing recovery options; the Computors will vote on the frozen funds and any compensation, according to Cointelegraph and investingLive. Restitution, a rollback or some other treatment of the frozen funds are all possible outcomes, and Qubic has not said which it favours.

Qubic’s record: the 2025 Monero hashrate push

Qubic is a layer-1 network with feeless transfers and smart contracts, founded by Sergey Ivancheglo, known as Come-from-Beyond, a co-founder of IOTA and NXT. It markets a “useful proof of work” meant to put its miners’ computing toward training an AI system. Most crypto users heard of it in 2025, for a different reason.

Between May and late July 2025, Qubic’s share of Monero‘s hashrate grew from under 2% to over 25%, CoinDesk reported. Qubic said it converted its XMR mining rewards into USDT and used them to buy and burn QUBIC. Around 12 August 2025 it claimed more than 51% of Monero’s hashrate, then said it had stopped short of taking over consensus because of what that would do to the XMR price.

Ledger CTO Charles Guillemet wrote on X that Monero “appears to be in the midst of a successful 51% attack”, The Block reported, and put the cost of keeping that dominance at about $75 million a day. BitMEX Research said it was unclear whether Qubic could sustain selfish mining, according to CoinDesk. XMR traded around $252 on 12 August, down 6% in 24 hours and 13.5% over seven days. Kraken paused XMR deposits as a precaution, citing a single pool with more than half of the network’s hashing power, while trading and withdrawals continued, CoinCodex reported. Qubic itself faced DDoS attacks on its peripheral services for over a week, CoinDesk said.

A month later, on 14 and 15 September 2025, Monero went through an 18-block reorganisation at height 3,499,659, erasing 36 minutes of history and invalidating 118 transfers, the biggest rollback in the network’s 12-year history, Decrypt reported. Observers tied it to a hidden chain released by Qubic’s pool. Qubic’s pseudonymous marketing lead, Retrodrive, reaffirmed the project’s “white hat” intentions, Decrypt wrote.

That episode was about Qubic’s mining power over another chain. The October 2026 theft is a plain software flaw in its own wallet. The two have nothing technical in common. What they share is the project, and the sight of exchanges restricting a coin while Qubic’s next move was awaited: XMR deposits at Kraken in 2025, QUBIC deposits and withdrawals at Bitget, MEXC and XT this week.

Weak randomness has emptied wallets before

The Qubic case belongs to a known family of failures, as Cointelegraph noted. In July 2026, Coldcard disclosed thefts from wallets whose seeds had been weakened by a firmware bug. In 2023, the Trust Wallet browser extension and Libbitcoin Explorer’s “bx seed” command were both found to generate seeds from weak randomness, and users of both lost funds.

Each time the pattern was the same: the cryptography of the chain held, and the weak link was the random source behind the key. For a related story about how much depends on where random-looking numbers come from, see our report on how Claude traced the NIST curve seeds to a 1997 clock.

Cointelegraph also cited AMLBot’s third-quarter 2026 report, based on 250 investigations opened since January: hacks and exploits made up 19% of the crypto crime cases but 40% of reported losses.

What is still unknown, and the next steps

Several points are open as of 19 October 2026. Nobody has published the attacker’s method, identity or the seven collecting addresses, or linked them to earlier thefts. Qubic has not explained why it singles out Apple environments. The number of wallets still holding weak seeds, and the value in them, is unknown. Qubic did not answer Cointelegraph’s request for comment, and its statement is known only through the outlets that quoted it.

No date has been given for any of the next steps: the restart of the chain, the Computor vote on the frozen funds and restitution, migration instructions for exposed wallets, MEXC’s decision on the 12.9% it froze, the reopening of QU deposits and withdrawals at Bitget, MEXC and XT, and the technical report Qubic says will follow its recovery plan.