zkLink Nova Bridge Exploit Drains About $779,000 in One Transaction

An attacker withdrew about $779,000 in $ETH and tokens from zkLink Nova's bridge on Ethereum in a single transaction on Oct. 28, according to onchain transfers reviewed by The Defiant.

Blockchain security firm Blockaid said the attacker used a public relayer to inject a forged batch root—a cryptographic summary used to verify messages—and then finalized withdrawals to attacker-chosen recipients. It described the attack as “still ongoing” in its alert at 10:24 p.m. ET on Oct. 28.

The main Ethereum escrow's read-contract page displayed its pause flag as false when checked at 10:29 p.m. ET. That reading does not establish whether other controls had blocked further attacks. A response from zkLink was not immediately available.

The withdrawal transaction, executed at 6:21 p.m. ET, transferred 22.43 $ETH from Nova's Ethereum escrow and 11 types of ERC-20 tokens from its token bridge to the same recipient. The largest component was 245.74 pufETH, valued by Etherscan at about $613,536. The transfers also included about 18,113 USDC and 3,361 USDT.

The Defiant calculated a combined value of $778,625.84 by adding the $ETH and token transfers at the prices displayed by Etherscan when checked at 10:25 p.m. ET. That is the value of this transaction, not a final tally for the incident.

Forged Root Opens the Withdrawal Path

Nova aggregates assets from Ethereum and its Layer 2 networks. Deposits are locked in contracts on their source chains and made available on Nova through its canonical bridge.

Under zkLink's documented settlement process, proof verification and cross-chain consistency checks precede finalization of a transaction batch. Its batch root is then sent to connected chains so withdrawals can proceed. Blockaid's account describes a forged root entering that authorization path.

The Ethereum transaction's logs show a new batch root being recorded before the $ETH and token withdrawal events in the same transaction. Etherscan subsequently showed roughly 0.001 $ETH remaining in the affected $ETH escrow.