LayerZero blames Kelp's setup for $290 million exploit, attributes it to North Korea's Lazarus

LayerZero has placed responsibility for the $290 million Kelp DAO exploit on Kelp's own security configuration, saying the liquid restaking protocol ran a single-verifier setup that LayerZero had previously warned against.

The attack used a novel vector targeting the infrastructure layer rather than any protocol code.

Attackers, whom LayerZero attributed with preliminary confidence to North Korea's Lazarus Group and its TraderTraitor subunit, compromised two of the remote procedure call (RPC) nodes that LayerZero's verifier relied on to confirm cross-chain transactions.

RPC nodes are the servers that let software read and write data on a blockchain, and LayerZero's verifier used a mix of internal and external ones for redundancy.

The attackers swapped the binary software running on two of those nodes with malicious versions designed to tell LayerZero's verifier that a fraudulent transaction had occurred, while continuing to report accurate data to every other system querying those same nodes.

That selective lying was engineered to keep the attack invisible to LayerZero's own monitoring infrastructure, which queries the same RPCs from different IP addresses.

Compromising two nodes was not enough. LayerZero's verifier also queried uncompromised external RPC nodes, so the attackers ran a distributed denial-of-service attack on those to force failover to the poisoned ones.

Traffic logs LayerZero shared show the DDoS running between 10:20 a.m. and 11:40 a.m. Pacific Time on Saturday. Once the failover triggered, the compromised nodes told the verifier a valid cross-chain message had arrived, and Kelp's bridge released 116,500 rsETH to the attackers. The malicious node software then self-destructed, wiping binaries and local logs.

The attack only worked because Kelp ran a 1-of-1 verifier configuration, meaning LayerZero Labs was the sole entity verifying messages to and from the rsETH bridge.

LayerZero's public integration checklist and direct communications to Kelp had recommended a multi-verifier setup with redundancy, where consensus across several independent verifiers would be required to confirm a message. Under that configuration, poisoning one verifier's data feed would not have been enough to forge a valid message.

"KelpDAO chose to utilize a 1/1 DVN configuration," LayerZero wrote, using the protocol's term for decentralized verifier networks. "A properly hardened configuration would have required consensus across multiple independent DVNs, rendering this attack ineffective even in the event of any single DVN being compromised."

LayerZero said it has confirmed zero contagion to any other application on the protocol. Every OFT-standard token and application running multi-verifier setups was unaffected.

The LayerZero Labs verifier is back online, and the company said it will no longer sign messages for any application running a 1-of-1 configuration, forcing a protocol-wide migration off single-verifier setups.