Approximately 23% of the Ethereum network has been taken offline due to an issue with the Prysm consensus client on the mainnet.
Early Thursday morning, the Ethereum Foundation alerted the community to an issue with the Prysm consensus client on mainnet and urged node operators to reconfigure their CL nodes. This only affects clients using the Prysm client, other network clients are not affected.
Ethereum client Prism said in a confirmation tweet that it had identified the issue and promised a quick workaround. Prompted dependent nodes to disable Prysm client.
Sasal ETH, an Ethereum angel investor and educator, revealed a shocking fact in a tweet following this incident.
A bug in the Ethereum Prysm client brought down about 23% of the network. Sasal shared an image along with the tweet, which showed that Prysm has about a 23% share of Ethereum consensus clients.
Commenting on the data presented, Sasal said it was accurate that the Prysm bug took about 23% of the network offline. He revealed a worse scenario that would have happened if a Lighthouse client had this issue.
According to the image, Lighthouse has a 48.47% share of Ethereum consensus clients, and Sasal added that if it was Lighthouse that had the bug, the ETH network would have lost finalization, which is not a good example for the Ethereum network.
Ethereum creator allays concerns
Ethereum founder Vitalik Buterin weighed in and dispelled such concerns. “It’s not a bad thing to fail to finalize once in a while,” Buterin said.
It’s okay to fail to finalize from time to time.
Finalization occurs when we are really sure that the block will not be undone. If there’s a bug in the main client and Finality is delayed for a few hours, that’s okay. Meanwhile, the chain continues.
Things to avoid…
— vitalik.eth (@VitalikButerin) December 4, 2025
Ethereum’s creators shed further light on the context of finalization, saying, “Finalization is something you do when you’re really confident that a block won’t be undone.”
Buterin allayed concerns about the Prysm incident, saying, “If finality is delayed for a few hours when there’s a bug in a major client, that’s OK. Meanwhile, the chain continues to move forward. What you want to avoid is finalizing the wrong thing.”
Fusaka, Ethereum’s second upgrade in 2025, went live on mainnet on December 3, marking a significant milestone for the network.
