Litecoin Rolls Back 13 Blocks After MimbleWimble Flaw Triggers Invalid Transactions
CoinMarketCap reported that Litecoin carried out an unusual 13-block chain reorganization after a MimbleWimble-related vulnerability enabled invalid transactions to propagate across parts of the network, disrupting hash rate and block times.
The issue was identified on April 25 and involves MimbleWimble Extension Blocks (MWEB), Litecoin's privacy-focused feature set. Attackers leveraged a flaw to push invalid MWEB transactions to nodes that had not upgraded to the latest software.
In an update posted by the Litecoin account, the project said a zero-day vulnerability was used to launch a denial-of-service attack that knocked major mining pools offline. It also warned that outdated mining nodes could accept invalid MWEB transactions, allowing attackers to "anchor" tokens to third-party DEXs. Litecoin said the 13-block reorganization reversed the invalid transactions and they will no longer appear.
According to the report, the compromised nodes treated malicious activity as valid, which could lead to unauthorized withdrawals to external decentralized platforms. The attack is described as particularly dangerous for cross-chain infrastructure, where double-spend risk is most acute.
Mining pools were also targeted, contributing to a sharp decline in network hash rate and impairing consensus performance. Average block time reportedly jumped from the normal 2.5 minutes to about 13.5 minutes, signaling severe network stress.
To contain the incident, Litecoin rolled back roughly three hours of chain history via the 13-block reorg. The Litecoin Foundation said legitimate transactions were preserved and the invalid MWEB activity was removed. The episode also renewed scrutiny of proof-of-work systems under extreme conditions and raised questions about settlement finality.
Early estimates put losses at around $600,000 for NEAR Intents, with the broader ecosystem total still being recalculated after the reorganization.
Market reaction has been limited. Litecoin slipped to around $55, pointing to short-term caution rather than widespread panic.
The incident is described as the first major attack on MWEB since launch, arriving amid a broader wave of security issues affecting projects such as Drift Protocol and Kelp, and may intensify debate among proof-of-work supporters.
As of April 26, the network had returned to normal operations following the release of a patch. Developers are urging node operators and miners to update immediately to reduce the risk of similar attacks.
