F2Pool mines 13 blocks to end Litecoin MWEB chain split

F2Pool mined 13 consecutive blocks to resolve a temporary split on the Litecoin network after an exploit allowed an attacker to fabricate a pegout for 85,034 LTC. The reorganization restored a single valid chain and took about two hours and 45 minutes to complete.

On April 25 a zero-day bug in Litecoin’s MimbleWimble Extension Blocks (MWEB) privacy layer let an attacker create a fraudulent pegout, a transaction type that moves coins from the MWEB layer back to the main Litecoin chain. The fake pegout claimed a withdrawal of 85,034 LTC. Nodes that had not updated their software accepted the invalid transaction, and the attacker used the outputs to move funds to decentralized exchanges.

The invalid transaction produced two competing versions of the blockchain and stalled several mining operations. Network participants worked to replace the chain that contained the invalid blocks with a longer chain that followed the corrected consensus rules. Onchain records show F2Pool mined all 13 consecutive blocks in the chain that became the valid ledger, providing the proof-of-work needed to orphan the attacker’s blocks and prevent irreversible exchange confirmations tied to the fraudulent transactions.

Litecoin developers released Core v0.21.5.4 to patch the inflation bug that allowed the fabricated pegout and to fix a mining node stall that contributed to the disruption. Operators of full nodes and mining rigs were urged to install the update so their software recognizes the corrected consensus rules.

After the reorganization and client update, the network resumed normal operation. Developers confirmed legitimate transactions were preserved and said they will continue monitoring for related issues and recommending that operators run the latest software to avoid accepting malformed MWEB pegouts.