Ethereum Fusaka Upgrade Faces Prysm Node Issues, Potentially Causing 382 ETH Losses

Ethereum

Ethereum Fusaka Upgrade Faces Prysm Node Issues, Potentially Causing 382 ETH Losses

Ethereums Fusaka upgrade on December 4, 2025, experienced Prysm node failures due to resource exhaustion from out-of-sync attestations, leading to missed epochs, an 18.5% missed slot rate, reduced network participation to 75%, and approximately 382 ETH in validator reward losses.

• Prysm nodes failed during heavy attestation loads in the Fusaka upgrade, causing about 18.5% missed slots across 42 epochs.
• Out-of-sync attestations forced extensive recomputations of historical beacon states, overwhelming node resources.
• Validators incurred 382 ETH in losses from delayed responses; Prysm issued fixes via config flags and software updates to prevent replays.

What Caused Prysm Node Failures During Ethereums Fusaka Upgrade？

Ethereum Fusaka upgrade Prysm failures stemmed from resource exhaustion during attestation processing on December 4, 2025. Out-of-sync attestations referencing outdated block roots triggered Prysm nodes to replay historical beacon states, leading to thousands of costly recomputations under high load. This caused widespread delays, missed epochs from 411439 to 411480, and significant validator impacts across the network.

How Did Out-of-Sync Attestations Lead to Resource Exhaustion？

During the Ethereum Fusaka upgrade, Prysm beacon nodes encountered attestations from potentially desynchronized nodes. These attestations pointed to block roots from prior epochs, conflicting with the current chain state. To adhere to Ethereums consensus rules, Prysm initiated full verification processes, which involved rebuilding older beacon states by replaying past blocks and executing epoch transitions.

This recomputation was computationally intensive. For instance, verifying an attestation tied to block 0xc6e4ff from epoch 411441 required multiple state transitions. Under concurrent high-volume attestations, nodes handled nearly 4,000 such operations, exhausting CPU and memory resources. The Prysm team reported that this led to nodes failing to respond to validator requests in time, amplifying the disruption.

Network-wide, the incident spanned 42 epochs, resulting in 248 missed blocks out of 1,344 slots—an 18.5% miss rate. Participation dipped to around 75% at its lowest, far below typical levels. Validators faced tangible penalties, with total missed attestation rewards amounting to about 382 ETH, as calculated by the Prysm team based on on-chain data.

Expert analysis from the Ethereum Foundation underscores the importance of client diversity in preventing such single-client vulnerabilities. Miga Labs data, referenced in Prysms post-incident review, showed a temporary shift in client distribution during recovery, highlighting ongoing risks if dominance by one client persists.