Ethereum delayed its Glamsterdam testnet fork over a gas flaw

Ethereum developers postponed the Glamsterdam activation on the Hoodi test network, which had been set for 23 October, after the auditing firm ChainSecurity reported findings a day earlier. The upgrade changes how the chain charges for creating and reading data through EIP-8037 and EIP-8038, adds a separate gas pool for new state and introduces block-level access lists so transactions can be verified in parallel.

What ChainSecurity found

The finding is about behaviour rather than a broken function. Repricing gas changes which operations run out of it, so a contract that was written to fail in a particular situation may now finish instead, permanently recording something it was designed to leave retryable. The firms most exposed are those that used gas checks as a safety mechanism. Every smart contract on the chain carries assumptions like that, and almost none of them are written down anywhere.

“Even with unchanged contract code, a failure path that previously reverted can now complete.”

— ChainSecurity, On the effect of the gas changes

ChainSecurity counted 13 real-world examples and began disclosing to the affected projects, with the Ethereum Foundation assessing how far the exposure goes. The number is small, and the category is the point: these contracts are immutable, so none of them can be patched.

Why gas repricing is different

That is what makes gas repricing a different kind of change from a normal upgrade. The assumption a deployed contract encodes is about the cost model of the chain underneath it. Change the model and the contract behaves differently without a line of its own code being touched, and its author may not be reachable.

The response was quick and unglamorous. Preston Van Loon shipped a Prysm client update that removes the upgrade, Christine Kim published guidance on downgrading, and no new Hoodi date has been set.

What the numbers say

One number puts the scale of the ambition in context. Mainnet's gas limit is 60,000,000, and the block we read while writing this used 28,399,214 of it, which is 47%. Glamsterdam on the Sepolia testnet on 6 October lifted the limit to nearly 200m, more than three times mainnet. The ceiling being raised is not the one currently binding.

Markets priced it correctly at nothing: ether sits at $2,399.34, down 0.16% on the day. A test network exists so this happens there, the same way the XRP Ledger patched an unlimited-issuance bug before it mattered, and the same way Solana moved its consensus switch one slot at a time this week. What settles this is a new Hoodi date and whether the end-2026 mainnet target survives.

Informational material, not investment advice. The flaw was found on a test network, no mainnet funds were at risk, and the final count of affected contracts has not been published.