Ethereum core developers have postponed the Glamsterdam upgrade on the Hoodi testnet, which was set for Oct. 26 at 17:42:48 UTC (epoch 132,352). The Ethereum Foundation said developers made the call on ACDE #248 "to allow for further investigation of interactions of EIP-8037 with mainnet smart contracts." No new activation date has been set.
The delay removes the Amsterdam execution layer and Gloas consensus layer activations. It also removes a schedule that would have raised Hoodi's gas limit to 200M. The change rolls back the configuration for a future upgrade and does not revert Hoodi's chain history.
What ChainSecurity found
The trigger was research from the security firm ChainSecurity. On Oct. 13 it warned that EIP-8037 and EIP-8038 could weaken defenses against insufficient gas griefing, an attack in which a malicious caller supplies too little gas on purpose.
⚠️ It has just been decided to delay the Glamsterdam hard fork on the Hoodi testnet because of security impacts we identified in this blog post: https://t.co/UCpy6Jp5Pa
— ChainSecurity (@chain_security) October 22, 2026
We already found 13 real-world examples and are in responsible disclosure with the affected projects.
Please…
Under the new rules, gas could be returned to a contract after an operation fails, so execution that once halted could continue. A contract could then permanently record a failed operation or erase a user's claim. ChainSecurity calculated that creating a new storage slot could take 110,020 gas when a separate allowance runs out, against 22,100 under the old rules.
The firm said it found 13 cases confirmed in real-world environments and is running responsible disclosure with the affected projects. It has not named them. It also said not every gas-related check would become unreliable, but developers would need to review their safeguards against the new rules.
Independent security researcher pcaversaccio called the risks "serious" in an Oct. 21 GitHub comment and asked for the fork to be reassessed. ChainSecurity has demonstrated the mechanisms but has not publicly established that a major production protocol is exploitable.
A schedule that has already slipped
Glamsterdam went live on Sepolia, the first public testnet, on Oct. 6. Developers fixed the Hoodi date at the ACDE #247 call on Oct. 8, with client releases due Oct. 16.
The calendar was already behind. Developers originally targeted the first half of 2026 and moved to the fourth quarter in mid-August, after the Platåberget test network went live. Sepolia was first scheduled for Aug. 3.
Developers had discussed early December for mainnet, though no date was formally adopted, and the delay complicates that planning. The official upgrade list, EIP-7773, still leaves the mainnet date blank.
What operators and developers should do
Hoodi node and validator operators need to check both their execution and consensus layer clients for instructions that reflect the postponement. Software or custom network configurations that still schedule Glamsterdam at the old time must be updated.
When the foundation posted, it listed releases for four clients. Lodestar v1.50.1, Besu 26.10.1 and Nethermind 2.2.1 were out, along with Ethrex v30.0.1-rc.2, a prerelease. The foundation warned operators not to treat the earlier announcement's release tables as confirmation that those versions include the postponement. It said to follow each client team's release notes.
Application developers should not plan Hoodi testing around Oct. 26. The foundation said the announcement concerns Hoodi only, and that "no action is required from Ethereum mainnet users or ETH holders".
The foundation has not detailed what the EIP-8037 interactions involve. Developers also have not said when Glamsterdam will return to Hoodi or whether the findings will change the proposed upgrade.
Tanya Petrusenko
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