Ethereum delays Glamsterdam Hoodi testnet fork after gas security findings

24 Oct 2026

24 Oct 2026, 01:58 UTC+02:00

Ethereum’s next major upgrade has hit a snag. Developers postponed the Glamsterdam activation on the Hoodi test network, which had been scheduled for 26 October at 17:42 UTC, after security firm ChainSecurity identified a problem with the upgrade’s new gas rules. The decision was taken during Thursday’s All Core Devs Execution call. No replacement date has been announced.

What went wrong

Glamsterdam changes how Ethereum charges for creating and accessing stored data through two proposals, EIP-8037 and EIP-8038, and introduces a separate gas pool for creating new state. The aim is to limit database growth as the network raises its capacity.

ChainSecurity found that these changes break assumptions many contracts rely on. Some contracts depend on a failed external call running out of gas so the whole transaction reverts. Under Glamsterdam, gas can be returned after a failed call, so “a failure path that previously reverted can now complete,” the firm wrote. That could let an attacker make a valid operation fail and be recorded permanently. The reverse can also happen: creating a new storage slot could cost 110,020 gas in some cases instead of 22,100, causing valid operations to fail.

ChainSecurity said it found 13 real-world examples and is in responsible disclosure with affected projects, while the Ethereum Foundation assesses how many contracts are exposed. CoinDesk notes there is no sign of current exploitation, since the rules are not live on mainnet.

Road to mainnet

Glamsterdam went live on the Sepolia testnet on 6 October with a gas limit near 200 million, more than three times mainnet’s 60 million. It also adds block level access lists for parallel checks and moves block builder selection into the protocol. Developers had aimed for a mainnet launch by the end of 2026. Node operators on Hoodi should revert to an older release or install client updates that cancel the fork.

What it means for traders

• Timeline risk: a later mainnet date can weigh on short term ETH narratives built around scaling.
• Good process, not a hack: the issue was caught on a testnet, which is what testnets are for.
• Trade ETH on solid venues: compare ETH fees in our crypto exchange fee index and platforms in our exchange comparison.

Sources

• Decrypt: Ethereum Delays Glamsterdam Testnet Fork Over Gas Security Flaws
• CoinDesk: Ethereum delays Glamsterdam test after security devs flag risk to existing contracts

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