Ethereum Prysm Fusaka Mainnet Postmortem: 42 Epoch Window Shows 18.5% Missed Attestations and 382 ETH Lost in Validator Rewards

COINOTAG News notes that Ethereum consensus layer client Prysm published a postmortem on the Fusaka mainnet incident dated December 4. During the upgrade, Prysm beacon nodes faced resource exhaustion while processing certain attestations, delaying validator responses and causing missed blocks. The event spanned epochs 411439–411480 (42 epochs), with 248 blocks missing out of 1,344 slots (~18.5%). Participation fell to 75%, and validators potentially lost ~382 ETH in rewards. The root cause: attestations from potentially out-of-sync nodes referencing the previous epoch’s block root, triggering repeated replay of stale epoch states under high concurrency.

Temporary mitigations included enabling the –disable-last-epoch-target parameter in v7.0.0. The follow-up releases v7.0.1 and v7.1.0 implement a long-term fix validating attestations against the head state, reducing upgrade risk.

Going forward, operators should keep node clients current and monitor upgrades. The postmortem offers a blueprint to strengthen resilience: head-state validation, safer concurrent attestations, and preserved block production.