On Friday and Saturday, a series of events unfolded on the Litecoin network, resulting in a 13-block reorganization that reversed approximately 32 minutes of network activity. This chain reorganization was triggered by an exploit of a vulnerability in the Mimblewimble Extension Block (MWEB) protocol, which allowed for a denial-of-service attack against major mining pools.
The exploit enabled invalid MWEB transactions to be processed by nodes that had not been updated. However, once the network's longest valid chain corrected these transactions, the issue was resolved.
In response to the incident, Litecoin Core version 0.21.5.4 has been released, which includes important security updates. According to the Litecoin Foundation, the bug has been fully patched, and the network is now operating normally. Nevertheless, some researchers argue that the timeline of events, as indicated by the litecoin-project GitHub repository, suggests that the vulnerability was known and privately patched between March 19 and 26, roughly four weeks before the attack.
This raises concerns about the window of vulnerability that existed due to the delay in publicly disclosing and implementing the patch across all mining pools. The attack highlights the differences in how various networks respond to exploits, with newer chains often being able to coordinate upgrades more quickly than older proof-of-work networks like Litecoin. The full extent of the damage caused by the exploit, including the amount of LTC pegged out and the value of any swaps completed before the reorganization, has not been disclosed.