Ethereum delays Glamsterdam's Hoodi test over smart contract gas risk

Ethereum developers have called off the Glamsterdam upgrade on the Hoodi test network, which was due on 26 October, after security researchers showed that its new gas rules could change how smart contracts already running on mainnet handle failed operations, CoinDesk reported. The decision was taken at Thursday's All Core Devs Execution call. No replacement date has been announced.

Hoodi was meant to be the final public rehearsal before mainnet, as we explained in our overview of what Glamsterdam changes. The upgrade had already gone live on the Sepolia testnet on 6 October.

What the researchers found

Security firm ChainSecurity published an analysis on 13 October about two of the upgrade's gas changes:

• EIP-8037 raises the cost of creating new entries in Ethereum's state, the database every node stores, to slow its growth as blocks get bigger.
• EIP-8038 reprices access to that state.

Together they change how much gas is left when one contract calls another that runs out of gas. Many contracts catch such a failure and carry on, for example recording that an attempt failed or switching off retries. Some rely on the leftover gas being too small for that step to finish, so the whole transaction reverts instead. Under Glamsterdam, gas spent on new records can be refunded when the change is undone, which may leave enough gas for that failure-handling step to complete. In an attack known as insufficient gas griefing, a caller deliberately sends too little gas, so a contract could permanently mark a user's valid claim as failed.

The risk runs the other way too. ChainSecurity calculated that creating a new storage slot could cost 110,020 gas once a separate allowance is used up, against 22,100 today, so a contract with a fixed gas budget might fail on an ordinary operation.

13 real contracts flagged

On Friday ChainSecurity said it had identified 13 real-world examples of potentially affected contracts and is coordinating responsible disclosure with the projects, without naming them. It has shown how the problem works but has not said that any major protocol can be exploited, and nothing is at risk today because the rules are not live on mainnet. Security researcher pcaversaccio called the risks "serious" in a GitHub comment on 21 October and asked for the fork to be reassessed.

What it means for the timeline

The planned rise of Hoodi's gas limit to 200 million is also on hold. According to Cointelegraph, developers had been eyeing early December for mainnet, to be confirmed after a successful Hoodi run; that now looks uncertain. Upgrades like this are coordinated hard forks, so every client has to ship the same rules before a new date can be set. Separately, researchers are working on a plan to cut Ethereum's finality to about four minutes.