zkLink Nova Bridge Forged-Root Exploit

On October 29, 2026, zkLink Nova — a Layer-3 aggregation rollup — had the Ethereum escrow securing its cross-chain bridge drained for approximately $786,000 in ETH and ERC-20 tokens. There was no stolen admin key and no obvious oracle to game: the attacker forged the very data that the bridge trusts to authorize withdrawals, and the Layer-1 contract paid out as if the request were legitimate.

What happened

According to security firm Blockaid, which flagged the attack on October 29, the exploit hinged on a forged batch root. Rollup bridges finalize cross-chain withdrawals by having the Layer-1 contract accept a Merkle root that commits to the batch of transactions processed off-chain; a valid root lets a user prove their withdrawal belongs to that batch. Here, the attacker used a publicly available relayer to inject a root the protocol had never produced, then finalized ETH and ERC-20 withdrawals to receivers of their own choosing. Because the Layer-1 contract accepted the forged root as authentic, the fraudulent withdrawals cleared normally, leaving zkLink Nova's main Ethereum custody contract nearly empty. Blockaid described the drain as still ongoing at disclosure, and stressed that the ~$786,000 figure was a running preliminary estimate rather than a final tally.

Aftermath

At the time of reporting, zkLink had not publicly confirmed the full scope of the loss, whether the affected contracts had been paused, or whether any funds could be recovered. No attacker identity was established and no recovery had been announced; the Ethereum escrow was reported to be essentially drained. The immediate open question was how a root that the protocol never generated came to be accepted by its Layer-1 verification path — a flaw in how submitted roots were validated, rather than a compromise of operator keys.

Why it matters

The zkLink Nova exploit is a reminder that a bridge is only as safe as the checks guarding what it will treat as a valid withdrawal proof. When the on-chain contract accepts an unverified or forged root submitted through an open relayer, the cryptographic machinery that is supposed to make withdrawals trustless instead rubber-stamps theft. It joins a long line of bridge failures where the loss came not from broken math but from a verification gap at the Layer-1 boundary, echoing cross-chain disasters like KelpDAO. For users, the lesson is blunt: bridge escrows concentrate value, and a single accepted lie about the state of an off-chain batch can empty them in one transaction.