A Forged Batch Root Drains zkLink Nova's Ethereum Bridge

A forged batch root submitted to Ethereum early on Thursday let withdrawals clear out of zkLink Nova's layer-1 escrow, and Blockaid, a security monitoring firm, flagged them while the attack was still running. The accounts that followed put the loss near $786,000 in one place and near $779,000 in another. They do not reconcile. What every account agrees on is the route: a publicly available relayer was used to submit a batch root the layer-1 contract then accepted, and ETH and ERC-20 withdrawals were finalised against it to an address the attacker controlled. No statement from zkLink had surfaced by Thursday morning.

How a batch root opens an escrow

zkLink Nova posts batches of transactions to Ethereum and holds the assets behind them in a layer-1 escrow contract. A batch root is the short commitment that stands for one of those batches; the contract checks withdrawal claims against it before paying out. Put a root in front of the contract that it accepts, and the claims underneath it clear. PANews, publishing at 02:27 UTC, describes exactly that sequence and names the public relayer as the way in. TokenPost gave the same account about two and a half hours later, naming the L1 ETH custody system and the ERC-20 bridge as the contracts involved. The Defiant attributes the mechanism to Blockaid rather than to its own reading of the chain, quoting the firm as saying a forged batch root had enabled unauthorised withdrawals.

Two totals, counted differently

PANews, the Phemex feed carrying it and TokenPost all give about $786,000, and all three call it the loss so far, with more possible while the attack was live. The Defiant gives about $779,000 and calls it one transaction, citing onchain records. Those are not the same measurement. One is a running tally taken during an incident in progress, the other is a single transfer. No account read here prints both, and we could not establish whether the smaller figure sits inside the larger. A KuCoin community post carried the number as $78.6 thousand, an order of magnitude below every other account, and nothing else supports it.

Several basic details are missing

None of the accounts read here itemises what was taken beyond ETH and ERC-20 tokens. None names the attacker's address. None gives the time the first forged root landed. The Defiant reports that the main Ethereum escrow still showed an unpaused status after Blockaid's warning, which rests on that single account and would matter a great deal if it held through the morning. A second headline on the Phemex feed describes the escrow as nearly empty; the body behind it could not be retrieved, so the claim is logged here and not used. The most recent account, published at 04:55 UTC, still described the incident as ongoing.

The failure mode, not the amount

Bridges lose money two ways: someone takes the key that authorises a mint or a withdrawal, or the proof the contract trusts turns out to be forgeable. This one is the second kind, and the sums involved are modest beside recent cases. CryptoJazz reported a stolen bridge key used to mint 260 million AGIX in September, and this month a bridge suspended after 10 million CYS appeared with no deposit. Scale is not what makes this one worth watching. A relayer open to anyone and a contract that accepted what it was handed is a combination that does not depend on how much was in the escrow at the time. What the desk is waiting on is zkLink's own account: the token breakdown, whether the escrow was paused and when, and a final total the two sets of reporting can agree on.