Litecoin’s MWEB Chain Split Resolved as F2pool Mines All 13 Blocks

Key Takeaways:

• f2pool mined all 13 blocks on the valid Litecoin chain, resolving the April 25 network split.
• An MWEB exploit let an attacker fake an 85,034 LTC pegout, triggering a 13-block reorganization.
• Litecoin Core v0.21.5.4 now patches both the inflation bug and the mining node stall behind the attack.

How the Exploit Unfolded

On April 25, the Litecoin network began processing invalid transactions on its MWEB layer, a privacy extension that lets users obscure transaction amounts and addresses. A zero-day bug in the code enabled an attacker to manufacture a fraudulent pegout, a mechanism that moves litecoin from the MWEB layer back to the main chain.

The malicious transaction fabricated a withdrawal of 85,034 LTC, creating an inflation vulnerability. Subsequently, non-updated nodes accepted the invalid transaction, and the attacker used it to redirect funds to third-party decentralized exchanges before developers could intervene.

The disruption, as expected, stalled several major mining pools and produced a temporary chain split, with two competing versions of the blockchain operating simultaneously. Following the event, Bitcoin.com offered comprehensive postmortem coverage, noting that developers moved quickly to freeze funds and coordinate a recovery response.

F2pool Steps in

Over approximately two hours and 45 minutes, mining pools coordinated to enforce the valid chain through a reorganization, a process where a longer valid chain replaces the one containing invalid blocks. Onchain data from ltc.supply confirmed that F2pool mined all 13 blocks in the winning chain, providing the consecutive proof-of-work needed to make the valid version the definitive record.

By rapidly marshaling an overwhelming majority of the network’s hash rate, the pool effectively orphaned the attacker’s blocks before irreversible exchange confirmations could be finalized.

Analysts described the effort as a “13-block chase” that helped the Litecoin network close the split and return to normal operation.

The Litecoin team confirmed all legitimate transactions remained intact throughout the incident. Litecoin Core v0.21.5.4 has since been released, addressing both the inflation bug that enabled the fraudulent pegout and the mining node stall that contributed to the disruption. The network is now operating normally.