MetaMask Security Breach Triggers Record Ethereum Validator Exits

A security breach affecting MetaMask-operated validators has led to a significant increase in Ethereum validator exits, with over 523,000 ETH leaving the network. This is the largest backlog of validator exits since December 2025, and it's putting pressure on the Ethereum staking infrastructure.

According to an onchain security researcher, Kaden, about 17,000 MetaMask-operated validators holding roughly 523,000 ETH were proactively exited after an analysis found that transaction-fee rewards from 18 of 19 validators that proposed blocks had been diverted to an address funded through Tornado Cash.

The attacker appears to have captured only about 0.36 ETH, but the bigger concern is how the attacker gained enough access to alter fee recipients and whether that access extended to validator signing keys, which could trigger slashable behavior.

MetaMask has not confirmed those figures or disclosed the cause of the incident, but it has said that part of its infrastructure had been compromised and that it was exiting affected validators as a precaution while working with clients, partners, and security advisers.