A network split has occurred on the world’s second-largest blockchain, Ethereum, after some network nodes failed to upgrade a patch to address a bug on the Geth network.

This created a fork between the mainnet and those that failed to update. In mid-August, developers of the Geth network —short for Go Ethereum — released a patch called “Hades Gamma” after they identified a bug impacting versions 1.10.7 of the network and earlier.

Geth represents almost three-quarters of all Ethereum nodes, and versions 1.10.7 or older represent almost 48% of all Geth nodes, as of press time. This means 35% of nodes have still not updated to the correct node.

Go Ethereum took to Twitter to address the split shortly after it occurred: “A chain split has occurred on the Ethereum mainnet. The issue was resolved in the v1.10.8 release announced previously. Please update your nodes, if you haven’t already!”

Until the split is resolved, it remains a big concern for any Ethereum-based application or investors in ETH. Information on blockchain technology is stored on the network in “chains” of transactions as they become verified, each adding to the ledger and the veracity of the network. A fork in this chain means the single chain has split into two potentially competing chains, meaning not all transactions are being verified by all nodes.

This increases the chances of a double spend, in which a single transaction is recorded more than once, allowing a user to misrepresent how much is in their wallet. Or a 51% attack, whereby a single entity controlling a majority of the hashrate of a proof-of-work blockchain is able to subvert it for their own gain.

A series of such attacks notoriously occurred on Ethereum Classic in August 2020, disrupting more than 10,000 blocks and costing millions of dollars in losses. More recently, the Bitcoin SV network suffered five 51% attacks between June and early August.

Fortunately, the impact of the split is likely to be minor, as the hashrate is being supported by the longest chain, and more nodes are updating to Geth 1.10.8 on an ongoing basis. This also means nodes running the older version of the network are unable to access the main network, though there have been no major incidents to report as of press time. If nodes continue to adopt the latest update quickly, the split should be rectified with little lasting impact to the network.

Martin Swende, security lead for the Ethereum Foundation, tweeted: “A consensus bug hit #ethereum mainnet today, exploiting the consensus-bug that was fixed in geth v1.10.8. Fortunately, most miners were already updated, and the correct chain is also the longest (canon). PSA: Update to v1.10.8!”        

Andre Cronje, founder of popular yield farming protocol Yearn Finance, had this advice for his Twitter followers: “Fork between latest geth and older geth on mainnet. Stay away from doing txs for a while till confirmed, unless you are sure you are submitting to latest geth.”

“Go for a walk outside, we all need it.”