Starknet releases post-mortem report: blockifier vulnerability caused transaction processing errors

Techub News reports that Starknet has released a post-mortem analysis of the brief mainnet outage on January 5. Starknet states that the core issue was a vulnerability in the blockifier, the block generator, which caused it to mishandle transactions. Specifically, in certain scenarios involving cross-function calls, variable writes, rollbacks, and rollback captures, the blockifier incorrectly recorded state write operations within rollback functions as valid, leading to transaction execution errors. However, thanks to Starknet’s proof layer mechanism, these erroneous executions never received finality confirmation on the L1 layer.

This incident triggered a blockchain reorganization, rolling back approximately 18 minutes of on-chain activity. This is the second major outage since 2025; the previous one in September was caused by a validator bug, resulting in over five hours of downtime and a rollback of about one hour of on-chain activity.