zkLink Nova Halts Block Production After Bridge Exploit Tops $780,000

zkLink Nova’s shutdown shows how quickly a flaw in bridge verification can become a network-wide incident. The network stopped producing blocks after attackers extracted more than $780,000 through contracts connecting Nova with Ethereum, while zkLink paused withdrawals and began reviewing the affected components. That combination matters: the reported exploit involved a path for moving assets across networks, while the response reached beyond the affected contracts and halted Nova itself.

The team said Thursday morning that it had deployed contract fixes, but offered no restart date, confirmed loss total or explanation of the exploit. “zkLink Nova services will only be restored after we have fully confirmed that all risks have been eliminated,” it said in an update on X. The statement sets a high bar for resuming service, but leaves users without a timetable or a detailed account of what the fixes address. Until the team explains the incident and its checks, the scope of the remaining uncertainty is hard to judge.

Earlier, zkLink said the attack targeted Nova’s Arbitrator contract on Ethereum and Optimism. It asked the attacker to return the funds and offered a “20% white hat bounty,” saying, “No further action will be pursued if funds are returned,” in a separate post. A public bounty offer can be a way to seek recovery, but it doesn’t establish whether the attacker will respond or how much of the money remains recoverable. The two messages also reflect different stages of the response: first an appeal to return funds, then a promise to keep services offline until risks are checked.

Transactions reveal multiple withdrawals

The first identified exploit transaction was confirmed at 6:21 p.m. ET on Oct. 28. It drew assets from two contracts: about 245.7 pufETH, valued at more than $600,000 at Thursday prices, plus 10 other tokens including roughly 12.6 ezETH, and approximately 22.43 ETH from Nova’s escrow. The mix of assets makes a single headline loss figure less straightforward to verify, since values depend on the prices used and the time of measurement. It also shows that the withdrawal affected more than one token balance.

Security firm SlowMist identified another transaction at 9:43 p.m. ET. A different wallet took 33 token types, mostly in small quantities; the largest component was about 216.4 million ZKL, zkLink’s token, worth roughly $50,000 at Thursday prices. Unchained confirmed the transfer on Ethereum. That wallet still held about 1.24 ETH and most of the tokens it withdrew. The reported balance is a snapshot, not proof that the assets will be returned or remain untouched. Still, it gives investigators a visible point of reference as they track what happened after the withdrawal.

A third withdrawal, around 0.0025 ETH, was recorded at 6:06 a.m. ET Thursday from another wallet, using steps similar to the first transaction. Unchained’s review covered Ethereum only, not Optimism. That limitation matters: the transactions described here don’t establish the full activity across every network involved. Small withdrawals can also be relevant to an investigation even when they barely affect the estimated total, because they may help show whether a method was repeated.

By 3:50 p.m. ET Thursday, Nova’s escrow contract showed a paused status, though the onchain data did not establish when the pause began. The wallet associated with the first transaction no longer held pufETH, USDC, USDT or WBTC, and had less than 0.001 ETH. About 2.5 mswETH and 2.6 mstETH remained. These balances describe what was visible at the time reviewed; they don’t explain where the assets that disappeared went or whether any can be recovered.

Security firms describe a forged batch root

Blockaid raised the alarm at 10:24 p.m. ET Wednesday, saying the attacker “used a public relayer to inject a forged batch root on Ethereum.” According to the firm, that enabled withdrawals of ETH and tokens to addresses selected by the attacker. Blockaid put the amount taken at about $786,000 while the drain was underway. In systems that rely on proofs to authorize cross-network withdrawals, the batch root helps establish which transactions should be accepted. If that verification can be manipulated, a withdrawal may appear valid to the contract even when it isn’t backed by legitimate activity.

SlowMist estimated the loss at approximately $783,100. Its analysis pointed to a function in the Arbitrator contract that allegedly allowed reuse of a valid message hash, installation of an attacker-chosen batch root and withdrawals backed by forged proofs. The explanation offers a possible chain of events, but zkLink has not confirmed either firm’s technical account or loss estimate. That distinction is important: outside analysis can help explain the evidence, while the project’s own account is needed to clarify what it found and how the fixes address it. The estimates are close, but they remain estimates.

What the outage means for users and the network

This is more significant than it looks. A bridge incident can affect confidence in the verification process that underpins asset transfers, while a chain shutdown adds a separate question about when users can interact with the network again. If you’re working in this space, the immediate concern isn’t only the amount reported stolen; it’s whether the project can explain the failure clearly enough for users to understand what has been fixed. And this is the part most people overlook: a contract patch and a safe restart are separate milestones.

Here’s the thing: pausing a network can limit further activity while a team investigates, but it also leaves users waiting for details about withdrawals and service restoration. zkLink hasn’t announced a restart date, and the source material doesn’t establish when one will be set. The company’s stated condition—confirming that risks have been eliminated—puts the emphasis on verification. That’s sensible in principle, though users will need more than a general assurance to assess what changed.

Nova’s outage follows a string of crypto incidents. A day earlier, Blockaid flagged a flash loan exploit that removed about $1 million in USDC from an Avalanche-based tranche vault. Earlier this month, Initia halted its chain after an attacker minted tokens and bridged out about $2.7 million, according to co-founder Zon, with no restart date announced. A Blockaid report also found hackers still hold $287 million in stolen crypto that cannot be frozen. Each case has its own mechanics, but together they underline how recovery and service continuity can remain unsettled after an exploit. No quick fix.

That said, the facts around Nova are still incomplete. The team has announced contract fixes and a cautious restoration condition, while security firms have published technical accounts and loss estimates that zkLink hasn’t confirmed. The next useful update will need to connect those pieces: what vulnerability was found, what was changed, and what users can expect as the network moves toward reopening. Until then, both the reported loss and the timeline remain open questions.

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