On Friday and Saturday, a 13-block chain reorganization occurred on the LTC network, undoing approximately 32 minutes of network activity after attackers exploited a vulnerability in the Mimblewimble Extension Block protocol. The bug enabled a denial-of-service attack against major mining pools, allowing invalid transactions to bypass nodes that had not been updated before the network's longest valid chain corrected them. Following the incident, Litecoin Core v0.21.5.4 was released, advising all users to upgrade due to important security updates. According to the Litecoin Foundation, the bug was fully patched by Sunday morning, and the network is now operating normally.
However, security researchers have pointed out that the timeline of events, as shown on the litecoin-project GitHub repository, indicates the consensus vulnerability was known and privately patched a month before the exploit. This created a window of vulnerability where some miners were running patched code, while others were still running the vulnerable version, which the attackers seemed to be aware of.
The attack involved a pre-funded wallet, a Binance withdrawal, and a decentralized exchange swap. The fact that the network automatically handled the 13-block reorganization after the denial-of-service attack stopped suggests that enough hashrate was running updated code to eventually overpower the attack. This incident highlights the differences in how various networks respond to exploits and the challenges faced by older proof-of-work networks like Litecoin in coordinating upgrades and patches among independent mining pools.