Starknet Outage: Understanding the Root Cause and Impact on the Ethereum Layer-2 Scaling Network
The Starknet team has released a post-mortem report on the recent outage that affected the mainnet, providing valuable insights into the root cause of the disruption. According to the report, the main cause of the mainnet downtime was a mismatch in the network state between the Blockifier execution layer and the verification layer. This mismatch occurred due to a specific combination of cross-function calls, variable writes, resets, and their interceptions, resulting in erroneous transaction execution.
The Starknet team explained that “in a particular combination of cross-function calls, variable writes, resets, and their interceptions, the blocker remembered a state write that occurred within a reset function, resulting in erroneous transaction execution.” An illustrated diagram of how the code flaw affected the network can be seen below: 
. Fortunately, the audit layer worked properly by flagging the error and not committing the erroneous transactions to the ledger.
Incident Response and Resolution
The incident forced a block reorganization and restoration of network activity for 18 minutes. StarkNet has returned to normal functionality, and the team has conducted testing and code audits to prevent similar issues in the future. The incident highlights the challenge of coding for the latest generation of blockchain networks, which include multi-layered technology stacks. For more information on how blockchain networks can be affected by outages, read about Iran’s internet outage and its impact on crypto.
Previous Disruptions and Lessons Learned
Monday’s outage was not the first disruption at Starknet in 2025. In September, StarkNet experienced a severe outage following a major protocol upgrade called Grinta. The outage lasted over five hours and was caused by a sequencer error, according to a postmortem report from the Starknet team. Sequencers are systems used to sequence transactions in a blockchain network. The outage can be seen in the graph below: 
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During the outage, block production was stopped, and two chain reorganizations were carried out to return the network to a functional state. The reorganization required about an hour of network activity to be undone or reset, meaning users had to resubmit transactions. While resubmitting a transaction may be a minor effort for some users, it can be disastrous for frequent traders or investors who need to exit a position or book a transaction in a short period. For a deeper dive into Ethereum’s technology, read Ethereum’s Fusaka Fork For Dummies Explained: What the Hell is PeerDAS?.
Cointelegraph is committed to independent, transparent journalism. This news article is produced in accordance with Cointelegraph’s editorial guidelines and aims to provide accurate and up-to-date information. Readers are advised to independently verify the information. Read our editorial policies here. For the full post-mortem report and more information on Starknet, visit https://cointelegraph.com/news/starknet-post-mortem-report-outage.
