Ethereum developers have fixed a flaw in the upcoming Glamsterdam upgrade that could have sent ETH meant for new validators to block builders.
The change entered Ethereum’s consensus specifications on October 26, after developers reconsidered a proposal they had rejected the previous week. The flaw concerned deposits waiting for processing when the network switches to Glamsterdam’s new rules.
No losses linked to the issue have been reported. The patch changes how Ethereum handles deposits during the upcoming Glamsterdam upgrade rather than any transfers already completed on Ethereum's main network.
Glamsterdam will separate block building from block proposal duties. Validators stake ETH to help secure the network, while builders assemble transactions into blocks. The upgrade introduces a separate deposit system for builders, although both roles can use the same public key.
Ethereum researcher avsetsin described a case where an operator first deposited ETH to register a builder. A staking service could then send ETH to create a validator using that same key. If both deposits remained pending at the upgrade, the proposed rules could direct the staking service’s money into the builder’s balance instead.
The operator could then withdraw the funds without creating the expected validator. That would also leave the staking service without the validator record needed for some recovery checks. In an October 12 GitHub report, avsetsin warned that “the operator can withdraw the protocol’s funds.”
The researcher examined possible exposure at Lido, Origin and Rocket Pool but cautioned that the checks were preliminary. “These are conditional code findings, not confirmed live exploits,” avsetsin wrote. Existing checks at some services could prevent the scenario.
The proposed correction initially failed to gain support. On October 19, Ethereum consensus-specifications maintainer Justin Traglia closed the issue after discussions with client developers. “There was not enough support from clients to make this change at this time,” Traglia wrote.
However, the delay to Glamsterdam’s next testnet deployment gave developers another chance to review the change. On October 23, contributor Dmitry Gusakov asked the team to revisit the problem because the upgrade timetable had changed. Traglia reopened the issue that day.
Avsetsin added regression tests to check how deposits would behave in different orders. On October 26, Traglia merged the revised code into Ethereum’s consensus specifications. The update routes deposits according to their withdrawal credentials, which identify the type of deposit and where withdrawals should go.
Under the revised rules, validator deposits remain in the validator queue even when a builder shares their public key. Builder deposits also follow their own path. Ethereum client teams must now implement these rules in the software that network participants run.
Glamsterdam activated on the Sepolia test network on October 6, allowing developers to examine its planned changes before a wider rollout. The next test was due on Hoodi on October 26, but Ethereum developers postponed that activation.
The Ethereum Foundation said on October 22 that developers needed more time to investigate how a separate gas-accounting proposal, EIP-8037, interacts with existing smart contracts. That concern was distinct from the validator deposit flaw. The foundation said Hoodi would receive a new schedule after further review.
For now, no revised Hoodi activation date or Ethereum mainnet launch date has been announced. Node operators must follow new client release instructions, while developers continue testing the rules for builders and validators before deployment.
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