Late Friday and Saturday, a chain reorganization of 13 blocks was initiated on the Litecoin network, effectively rewinding 32 minutes of network activity. This move was a response to an attack that leveraged a vulnerability in the Mimblewimble Extension Block protocol, enabling a denial-of-service attack against major mining pools and allowing invalid transactions to temporarily slip through nodes that had not been updated.
The Litecoin Core v0.21.5.4 release has been issued, advising all users to upgrade due to important security updates. 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 a month prior to the attack.
The consensus vulnerability was patched between March 19 and March 26, while a separate denial-of-service vulnerability was addressed on April 25. Both fixes were included in the release 0.21.5.4, which was rolled out after the attack had begun.
The incident highlights the challenges faced by older proof-of-work networks like Litecoin, where independent mining pools have the discretion to choose when to upgrade, potentially creating windows of vulnerability. The exact amount of LTC affected during the invalid block window and the value of any swaps completed before the reorganization remain undisclosed.