Ethereum Delays Glamsterdam Hard Fork on Hoodi Testnet After Gas Security Warnings

The Glamsterdam hard fork's activation on the Hoodi testnet has been put on hold by Ethereum's developers, following warnings from security researchers that planned changes to gas accounting could weaken protections built into existing smart contracts.

The Ethereum Foundation said the Hoodi activation, which had been set for 26 October, would be pushed back so developers could examine how some of the upgrade's proposals interact with contracts already deployed on the network.

What prompted the delay

The concerns trace back to an analysis published on 13 October by blockchain security firm ChainSecurity. It flagged two proposals bundled into Glamsterdam, EIP-8037 and EIP-8038, as potentially undermining safeguards against a class of exploit known as insufficient gas griefing.

According to ChainSecurity, the new rules could allow gas to be handed back to a contract after an operation inside it fails. That would let the contract keep executing in situations where, under current rules, it would have halted.

The firm said this matters because many contracts rely on checks tied to how much gas remains during a transaction. If the arithmetic behind those checks changes, the protections they were designed to provide may no longer hold.

ChainSecurity later said it had found 13 real-world cases of contracts that could be affected and was working through responsible disclosure with the projects involved. It did not name the projects or describe the individual cases, but urged developers to review their contracts promptly.

How insufficient gas griefing works

Every operation on Ethereum consumes gas, a unit that measures computational work. The caller of a transaction decides how much gas to supply, and if that amount runs out, the relevant operation fails.

In an insufficient gas griefing attack, a malicious caller deliberately supplies too little gas for a legitimate operation to complete. The goal is not necessarily to steal funds directly, but to cause a valid action to fail in a way that harms another user or leaves the contract in an unintended state.

Developers have long defended against this by checking remaining gas and refusing to proceed, or reverting, when there is not enough to finish safely. ChainSecurity's warning is that Glamsterdam's proposed gas changes could weaken those defences, so a contract might permanently record an operation as failed when it should have reverted.

The firm offered an illustration: an affected contract could delete a user's claim, or switch off the option to retry it, leaving that user unable to complete an action that would otherwise have been valid. For applications that handle withdrawals, rewards or other entitlements, that kind of silent, irreversible failure is a serious design flaw.

ChainSecurity was careful not to overstate the problem. It said Glamsterdam would not render every gas-based security check unreliable. Some safeguards would continue to function, but developers would need to re-examine them to confirm they account for the new rules.

Why it matters for Ethereum's roadmap

The delay introduces uncertainty into Glamsterdam's path to mainnet. Developers had been weighing an early-December activation and intended to fix a firm schedule once testing on Hoodi had gone smoothly. With Hoodi now on hold, that sequence has been interrupted.

Ethereum upgrades typically move through a series of public testnets before reaching the main network. Glamsterdam had already gone live on Sepolia on 6 October, and Hoodi was meant to be the next step. Testnets exist precisely to catch problems before real value is at stake, so a pause at this stage can be read as the process working as designed rather than a breakdown.

Still, the episode highlights a recurring tension in protocol development. Changes to gas pricing and accounting are often aimed at making the network more efficient or fairer in how it charges for resources. Yet thousands of contracts were written against the old rules, sometimes with assumptions their authors never documented. Altering those foundations risks breaking behaviour that developers took for granted.

This is not the first warning about Glamsterdam's gas model. The Ethereum Foundation had previously cautioned that the changes could break wallets, indexers and gas estimators that rely on fixed assumptions about costs. ChainSecurity's findings extend those concerns from off-chain tooling to on-chain security, which is a more sensitive area because deployed contracts often cannot be easily modified.

Reaction and counterpoints

The research drew concern from Ethereum contributors. Writing on GitHub on 21 October, pcaversaccio, a security researcher who uses a pseudonym, characterised the dangers as "serious" and urged that the hard fork be looked at again.

There are reasons for caution in interpreting the scale of the issue. ChainSecurity has identified 13 examples, but without details on which projects are involved or how much value they hold, it is difficult to gauge the practical exposure. Some of the affected contracts may be small or little used; others could be more significant. Responsible disclosure means that information is likely to remain private until fixes or mitigations are in place.

It is also worth noting that the firm's own analysis stops short of declaring gas-based checks broken across the board. The risk depends on how individual contracts were written, which means the burden of review falls unevenly across the ecosystem.

Developers face a choice about how to respond. One option is to adjust or drop the two proposals so that existing safeguards remain valid. Another is to keep the changes and rely on contract authors to audit and update their code. The second route preserves whatever benefits the proposals were intended to deliver, but places significant work on teams that may not be actively maintaining older contracts, and some contracts may be immutable.

What to watch next

The Ethereum Foundation has not, based on the available reporting, set a new date for the Hoodi activation. The key question is whether developers treat the findings as grounds for a short delay or for a more substantial rethink of Glamsterdam's gas changes.

Points to monitor include:

• Whether EIP-8037 and EIP-8038 are modified, removed or retained in their current form
• A revised Hoodi schedule and any knock-on effect on the early-December mainnet window
• Disclosures from ChainSecurity or affected projects once the responsible disclosure process concludes
• Guidance for developers on which gas-related checks need to be reviewed

For developers and protocol teams, the immediate message from ChainSecurity is straightforward: check contracts that depend on remaining-gas logic before the new rules reach mainnet. For the wider market, the pause is a reminder that Ethereum's upgrade timelines remain contingent on testing outcomes, and that changes to low-level mechanics can carry consequences well beyond their stated aims.