A security firm found that Glamsterdam's gas-pricing changes can make some existing smart contracts behave in unsafe ways, with 13 real-world examples so far. The Oct. 26 test activation is off, and no new date has been set.
Ethereum developers have delayed the Glamsterdam upgrade on the Hoodi test network, the last public test environment before mainnet, after a security review found that the upgrade could change how some existing contracts behave.
"It has just been decided to delay the Glamsterdam hard fork on the Hoodi testnet because of security impacts we identified," security firm ChainSecurity said on Thursday. "We already found 13 real-world examples and are in responsible disclosure with the affected projects." The firm urged developers to check their contracts, adding that the Ethereum Foundation is determining how many are affected and in what way.
The Hoodi activation had been scheduled for Oct. 26 at 17:42:48 UTC, at epoch 132,352, with the gas limit raised to 200 million. The Ethereum Foundation confirmed the postponement on its blog on Thursday, following the core developers' execution-layer call. No replacement date has been announced, and node operators have been told to run client versions without the fork.
What actually goes wrong
The issue lies in how Glamsterdam reprices gas, the fee paid for computation on Ethereum. Some contracts include a fallback path that is meant to fail if a transaction runs short of gas. Under the new rules, ChainSecurity found, "gas refills and repricing can let failure handlers complete where they once reverted, undermining assumptions behind existing gas checks." In plain terms, code that was written to stop under certain conditions might keep running instead.
The firm's review focused on two proposals in the upgrade, EIP-8037 and EIP-8038. The Ethereum Foundation had flagged the broader risk in August, when it said a replay of the repricing showed "a small set of smart contracts rely on assumptions the new schedule shifts."
Nothing has been exploited. The upgrade has not gone live on any network with real funds, and the affected projects have not been named.
What the delay means for timing
Ethereum has not set a mainnet date. Developers had listed Dec. 8 and 9 as candidate dates, but only as options. Fixing the problem means either changing the gas proposals or giving contract teams time to patch, and either route is likely to push mainnet activation past those early-December options.
Glamsterdam carries the network's main scaling changes for this cycle, including enshrined proposer-builder separation, block-level access lists and the gas repricing itself. A slip affects the scaling timeline that has been part of the case for ether ETFs and corporate ether treasuries.
Ether traded at about $2,377 at 1:51 p.m. Eastern, down 3.8% on the day, but the delay broke into a broad crypto selloff, so the move cannot be tied to it.
What to watch
A new Hoodi date from the core developers, and any change to EIP-8037 or EIP-8038. The size of the affected contract set will determine whether this is a short pause or a redesign.