Ethereum Sepolia Testnet Faces Challenges After Pectra Upgrade

According to Cointelegraph, the recent Pectra upgrade on Ethereum's Sepolia testnet encountered significant errors, exacerbated by an attacker exploiting an edge case to mine empty blocks. The upgrade was implemented on March 5 at 7:29 am, but Ethereum developer Marius van der Wijden reported on March 8 that error messages began appearing on their geth node, leading to the mining of empty blocks. The issue stemmed from the deposit contract triggering a transfer event instead of a deposit event. Although a fix was deployed, van der Wijden noted that they overlooked one edge case, which an unknown user exploited by sending a 0-token transfer to the deposit address, causing the error to resurface. "After a few minutes, we saw a lot of empty blocks again, so we looked into the transaction pools and found another offending transaction that triggered the same edge cases," he explained. Initially, the team suspected a mistake from trusted validators, but it was soon discovered that the transaction originated from a newly funded account via the faucet. The ERC-20 standard does not prohibit zero token transfers, allowing anyone to transfer tokens to another address, which the attacker utilized. "The only way to stop the attack would be to filter out all transactions that interact with the deposit contract. So we made the following private fix, which we deployed to a few of the DevOps nodes," van der Wijden stated. By 2 pm, all nodes were updated with the fix, and the problematic transaction was successfully mined. Van der Wijden assured that finalization was never lost during the incident, and the issue was confined to Sepolia due to the use of a token-gated deposit contract instead of the standard mainnet deposit contract. The Pectra upgrade had previously been tested on the Holesky testnet on February 26, which also faced challenges. Consequently, developers have decided to delay the Pectra upgrade until further testing can be conducted. The Pectra fork follows the network's Dencun upgrade, which reduced transaction fees for layer-2 networks and enhanced the economics of Ethereum rollups. The Dencun hard fork was rolled out on March 13, 2024. Additionally, the Ethereum Foundation has introduced a new leadership structure, appointing Hsiao-Wei Wang and Tomasz Stańczak as co-directors.