A significant disruption occurred on the Litecoin network late Friday and Saturday, resulting in a 13-block reorganization to reverse the effects of a denial-of-service attack. This attack exploited a vulnerability in the Mimblewimble Extension Block (MWEB) protocol, allowing invalid transactions to bypass nodes that had not been updated. The Litecoin Core v0.21.5.4 release, which includes crucial security updates, has been made available, and all users are advised to upgrade. According to the Litecoin Foundation, the bug has been fully patched, and the network has returned to normal operation.
However, security researchers have pointed out discrepancies in the timeline of events, suggesting that the vulnerability was known and privately patched between March 19 and 26, roughly four weeks before the attack. The consensus vulnerability and a separate denial-of-service vulnerability were both addressed in the release 0.21.5.4, which was made available after the attack had begun.
The incident highlights the challenges faced by older proof-of-work networks like Litecoin, where independent mining pools are responsible for upgrading, creating a window of vulnerability in the event of a security patch. The attack on Litecoin demonstrates the differences in how various networks respond to exploits, with newer chains often coordinating upgrades more quickly due to their smaller, more centralized validator sets.