Ethereum developers have officially decided to postpone the deployment of the upcoming Glamsterdam hard fork on the Hoodi testnet. The decision was reached after prominent blockchain security researchers identified critical, gas-related security vulnerabilities that could drastically alter how existing smart contracts handle failed transactions, introducing potential risks to millions of dollars in decentralized applications across the ecosystem.
The Ethereum Foundation (EF) announced that the upgrade, which was originally scheduled to go live on October 26, would be delayed indefinitely. This precautionary pause will allow core developers, client teams, and security researchers ample time to investigate how specific upgrade proposals interact with already deployed smart contracts operating on the Ethereum network.
The security concerns trace back to a vital warning issued on October 13 by blockchain security firm ChainSecurity. According to their published analysis, two specific proposals included within the broader Glamsterdam upgrade package—designated as EIP-8037 and EIP-8038—could inadvertently weaken established safeguards against a sophisticated type of blockchain vulnerability known as insufficient gas griefing.
This unexpected postponement introduces significant uncertainty over the overarching mainnet deployment timeline for Glamsterdam. Prior to this security discovery, Ethereum developers had been actively considering an early December launch date for the mainnet, with final scheduling decisions entirely dependent upon a smooth and successful testing phase on the Hoodi testnet. With the Hoodi deployment now on hold, the timeline for the mainnet release remains up in the air as developers prioritize network safety above strict launch deadlines.
Gas Changes Could Undermine Existing Smart Contract Safeguards
At the heart of the controversy is how the proposed changes alter the fundamental mechanics of gas handling during transaction execution and failure. In its comprehensive security analysis, ChainSecurity explained that under the new rules introduced by the upgrade, unused gas could potentially be returned to a smart contract immediately after an operation fails. Under current network rules, such a failure would typically cause the transaction execution to halt entirely. However, the proposed modifications could allow the contract to continue running its code when it otherwise would have stopped.
The researchers emphasized that these unexpected behavior changes could severely interfere with existing security checks written into smart contracts, which heavily rely on precise tracking of how much gas remains available during the lifecycle of a transaction.
In attacks commonly referred to as insufficient gas griefing, a malicious caller deliberately provides just enough—or rather, too little—gas for a legitimate smart contract operation to succeed, while still forcing the transaction to consume resources. ChainSecurity warned that Glamsterdam’s proposed modifications could undermine the defensive safeguards built to protect against such malicious interference. If exploited, this could potentially allow contracts to permanently record failed operations as processed, leading to severe unintended consequences for end users.
For example, an affected decentralized finance contract could incorrectly interpret a failed state change, automatically removing a user’s legitimate claim or permanently disabling the option to retry the transaction. This would leave the user entirely unable to complete an otherwise valid financial operation, locking them out of their funds or intended actions until manual intervention—if even possible—is executed.
ChainSecurity clarified that the Glamsterdam upgrade would not render all gas-related security checks completely unreliable. Certain foundational safeguards would continue to function as intended. Nevertheless, the firm stressed that smart contract developers across the ecosystem would need to thoroughly review their existing codebases to ensure they properly account for the upgrade’s novel gas rules before the changes hit the mainnet.
The severity of these findings quickly prompted deep concern among core Ethereum contributors and the broader developer community. In an online comment posted to GitHub on October 21, pseudonymous security researcher pcaversaccio described the identified risks as serious and explicitly called for a formal reassessment and re-evaluation of the hard fork’s parameters.
Adding to the urgency, ChainSecurity revealed on Friday that its ongoing investigations had successfully uncovered 13 real-world examples of vulnerable smart contracts currently exposed to these risks. The security firm noted that it was actively coordinating responsible disclosure efforts with the affected projects to help them mitigate the danger. While ChainSecurity chose not to disclose specific details regarding the 13 real-world examples or publicly identify the affected projects due to security protocols, the firm issued a stern reminder that application developers should audit their contracts as soon as possible.
These latest security discoveries follow closely on the heels of an earlier warning issued by the Ethereum Foundation itself. In that previous advisory, the Foundation cautioned that Glamsterdam’s shifting gas model could potentially break various developer tools, third-party wallets, blockchain indexers, and gas estimation utilities that rely heavily on fixed assumptions about how the Ethereum Virtual Machine handles execution costs and gas refunds.
Before the Hoodi delay was announced, the Glamsterdam upgrade had already been successfully activated on the Sepolia testnet on October 6, marking the beginning of its public testnet lifecycle before encountering these significant roadblocks on the path to Hoodi.
