Ethereum Delays Glamsterdam Hoodi Testnet Activation After Security Researchers Flag Risk to Existing Contracts

Developers called off Monday's activation after ChainSecurity showed how proposed gas rules could let smart contracts permanently record failed operations.

Ethereum developers have postponed the Glamsterdam upgrade on the Hoodi test network after security researchers found that proposed gas-accounting changes could alter how existing smart contracts handle failed transactions — in some cases allowing errors to become permanently recorded on-chain.

The upgrade had been scheduled to activate on Monday, Oct. 26, at 17:42:48 UTC. The delay was decided during Thursday's All Core Devs Execution meeting, where developers agreed to first investigate how the proposed changes interact with contracts already running on Ethereum's main network. No replacement date has been announced for the Hoodi test or for its planned increase of the gas limit to 200 million, and the timing of the upgrade on mainnet remains unconfirmed.

Hoodi is one of Ethereum's public test networks — environments where upcoming upgrades run on the same client software as mainnet before real funds are at stake. Surfacing unintended interactions like this one is the kind of issue the rehearsal step exists to catch before a change reaches the main network.

What the researchers found

The concern centers on EIP-8037, which changes how Ethereum charges for creating new records in its state database. The proposal is designed to limit the growth of that database as the network increases the number of transactions it can process.

Security firm ChainSecurity published an analysis of the proposals on Oct. 13, showing that the change, combined with EIP-8038, could alter how contracts respond when another contract they call runs out of gas — the resource used to pay the network's operators for computation.

Some smart contracts are designed to catch a failed operation and continue processing. They may record that an attempt failed, disable further attempts or move on to another step. Developers sometimes rely on the remaining gas being too low for those actions to finish, causing the entire transaction to reverse instead.

Glamsterdam changes that calculation. Under the proposed rules, gas used to create certain records can be restored when those changes are undone. That can leave a contract with enough gas to complete a failure-handling routine that would previously have run out of gas and reversed — meaning an error a developer intended to be temporary could instead become permanent. Because deployed contracts generally cannot be rewritten after the fact, such behavior changes have to be resolved in the protocol itself rather than in application code.

ChainSecurity also identified a risk in the opposite direction. It calculated that creating a new storage slot — the basic unit of a contract's on-chain data — could require 110,020 gas once a separate allowance is exhausted, compared with 22,100 under the current rules. A contract operating within an existing gas budget might therefore fail while carrying out an otherwise valid operation.

The findings concern how existing software would behave under the proposed rules. ChainSecurity has demonstrated the mechanisms but has not publicly established that any major production protocol is exploitable. Ethereum's mainnet has no confirmed Glamsterdam activation date, and the findings do not indicate that existing contracts are currently being exploited through the proposed changes.

Where Glamsterdam stands

Glamsterdam brings several changes to Ethereum, including a new system for choosing block builders and improvements intended to allow the network to handle larger blocks. The upgrade completed its Sepolia testnet activation on Oct. 6. Hoodi was set to be the next public rehearsal, alongside a planned increase in the testnet's gas limit to 200 million — a step that has also now been postponed.

With no replacement date set, the schedule now hinges on the agreed investigation into how the proposals interact with deployed contracts. Any revised Hoodi activation or mainnet timing would be settled at future All Core Devs meetings — the same venue where this week's delay was decided.

This article is based on reporting first published by CoinDesk: Ethereum delays Glamsterdam test after security devs flag risk to existing contracts. ChainSecurity's full analysis is available here.