Qubic halts mainnet after seed exploit drains 1,404 wallets

An attacker drained 1,404 Qubic user wallets of roughly 2.94 trillion QU tokens, worth about $1.3 million at the time, prompting the network to pause its mainnet on October 18, 2026.

A flaw in the wallets, not the chain

Qubic's developers traced the exploit to weak, predictable wallet recovery seeds created on legacy Apple devices, Safari browsers and early iOS applications. A seed is the secret string from which a wallet's keys are generated; where the generator draws too little randomness, attackers can reproduce the same seeds and the wallets they unlock. The team said the flaw sat outside the network's code, and it released client version 4.26.4 to fix seed generation. Developers also said they secured additional funds exposed to the same weakness before they could be taken, and that QEARN, the network's staking feature, was untouched.

The attack ran from 23:42 UTC on October 17 to 01:26 UTC on October 18, a window of about one hour and 44 minutes.

Validators stopped the chain

Qubic's validators halted the chain at tick 85,371,949 to freeze the stolen tokens. About 87.1% of the drained QU never left the network and is immobilized on-chain, while the remaining 12.9% reached the MEXC exchange, which froze the receiving account within an hour on suspicion it was tied to the attack. The 87.1% figure comes from the most detailed account of the drain; another outlet covering the story said only that most funds were frozen. MEXC and Bitget both suspended QUBIC deposits and withdrawals on October 18: MEXC said its suspension was requested by the Qubic project team, and Bitget cited wallet maintenance.

Whether the 1,404 affected users are reimbursed now rests with Qubic's validator cluster, and affected users are being told to file police reports. The mainnet restart date on the patched client has not been announced.

The incident is the second this year to hit Qubic through a component adjacent to its core, after the Vottun Bridge was exploited in August 2026, and it underlines a risk that reaches past this one network: wallet software that generated weak seeds on older Apple devices and browsers leaves those funds exposed regardless of how sound the chain itself is.

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