Ethereum confirms Glamsterdam dates, but warns 'fake' builders could stall the chain
Free test ether lets fake builders outbid rivals and withhold transaction payloads, while client teams get half the usual review time before Sepolia.
A teenager with free test ether and a collection of disposable builder identities could repeatedly win Ethereum’s new block auctions and refuse to deliver the transactions, developers warned as they confirmed an Oct. 6 public test of the Glamsterdam upgrade.
The attack would not endanger mainnet funds. It targets Sepolia, where test ether has no meaningful cost, but could leave blocks without transaction payloads and derail the infrastructure testing needed before Glamsterdam reaches Ethereum itself.
Glamsterdam moves the relationship between validators and specialized block builders into Ethereum’s protocol. Builders assemble transaction blocks and compete to supply them. Once a validator accepts the winning bid, the builder is expected to reveal the underlying transactions.
Developers said existing safeguards typically fall back to locally built blocks only after several payloads go missing. Potuz argued that clients also need to identify and reject individual builders so an attacker cannot return under a new identity and continue winning.