TechFlow, Dec 14 — The Prysm team, an Ethereum consensus layer client, released a post-mortem report on the Fusaka mainnet incident, following a network outage that occurred on December 4.
During the incident, nearly all Prysm nodes exhausted system resources when processing specific attestations, causing failure to respond timely to validator requests. The impact spanned epochs 411439 to 411480, resulting in 248 missed blocks over 42 epochs—a miss rate of 18.5%. Network participation dropped as low as 75%, and validators lost approximately 382 ETH in attestation rewards.
The root cause was Prysm beacon nodes receiving attestations from potentially unsynchronized peers referencing block roots from prior epochs. To validate these attestations, Prysm attempted to reconstruct compatible states, triggering repeated processing of past epoch blocks and expensive re-computation during epoch transitions.
The team provided temporary mitigation by advising users to adopt the --disable-last-epoch-target parameter. Long-term fixes have since been included in versions v7.0.1 and v7.1.0.
