TechFlow News, on June 27, the Base engineering team released a post-mortem report regarding the block production interruption that occurred on June 25.
According to the report, Base Mainnet experienced two separate block production interruptions—at 11:47 AM ET on June 25 and at 11:28 AM ET on June 26—lasting 116 minutes and 20 minutes respectively. The official statement confirmed that both incidents stemmed from the same technical issue; chain integrity remained unaffected, and user funds were never at risk.
The root cause, per the investigation, was a vulnerability in the Sequencer’s block construction logic. Specifically, upon transaction validation failure, the system failed to correctly clear expired log state information.
More precisely, when an invalid transaction was received by the block builder, it failed as expected—but the system erroneously retained account and storage slot access records associated with that transaction. Subsequently, another valid transaction executed without cleaning up the relevant state, causing inconsistencies in gas accounting and ultimately producing an ordered block containing invalid state transitions.
Because other nodes could neither verify nor accept this block, network consensus was halted, resulting in a complete stoppage of on-chain block production.
During the incident, Base was unable to generate new Layer 2 blocks; neither the sequencer nor the verifier nodes could bypass the invalid block to proceed, and users’ newly submitted transactions failed to be committed to the chain.
The Base team subsequently deployed a patch to the sequencer to ensure log state updates are handled correctly during execution, thereby restoring normal network operations.
Officially, the team stated that it will further strengthen protocol fuzz testing and stress testing capabilities to detect potential vulnerabilities triggered by adversarial transaction patterns earlier. Meanwhile, the team will continuously optimize operational procedures and monitoring systems to enhance network stability and incident response capability.
