Late Friday and Saturday, a chain reorganization of 13 blocks on the Litecoin network occurred at a value of $55.40, effectively rewinding 32 minutes of network activity. This was in response to an attack exploiting a vulnerability in the Mimblewimble Extension Block (MWEB) protocol, allowing for invalid transactions to bypass updated nodes before the network corrected them.
The Litecoin Core v0.21.5.4 release has been made available, containing crucial security updates and advising all users to upgrade. According to the Litecoin Foundation, the bug has been fully patched, and the network is now operating as normal.
However, security researchers have pointed out discrepancies in the timeline of events, suggesting the vulnerability was known and privately patched between March 19 and 26, more than four weeks before the attack. The consensus vulnerability and a separate denial-of-service vulnerability were both fixed in release 0.21.5.4 after the attack began. The term 'zero-day' refers to a vulnerability that was unknown to defenders at the time of the attack, but in this case, the commit history indicates the consensus vulnerability was known and patched a month prior to the exploit. This created a window of opportunity for attackers, who seemed to be aware of which miners were running patched code and which were still vulnerable.
Concerns have been raised regarding the exploit, with some arguing that the denial-of-service attack and the MWEB bug were separate components designed to take patched mining nodes offline. Blockchain data revealed that the attacker had pre-funded a wallet 38 hours before the exploit, intending to swap LTC for ETH on a decentralized exchange. The automatic handling of the 13-block reorganization by the network once the DoS stopped suggests that enough hashrate was running updated code to eventually overpower the attack.
This incident highlights the differences in how code maintainers and developers react to exploits across various networks, with newer chains often coordinating upgrades more swiftly than older proof-of-work networks like Litecoin and Bitcoin.