Litecoin Addresses Zero-Day Vulnerability and Releases Security Update

Litecoin Currently, Litecoin has drawn attention due to a suspected zero-day vulnerability, raising concerns within the cryptocurrency community. In response, the Litecoin developers have released an updated statement outlining the details of the incident. The official Litecoin Twitter account on X summarized the situation in a five-point .

Litecoin officially stated that a zero-day vulnerability triggered a denial-of-service attack, causing major mining pools to go offline. Subsequently, unupdated mining nodes allowed an invalid MWEB transaction, enabling these nodes to anchor Litecoin to a third-party decentralized exchange (DEX). After a 13-block reorganization, these invalid transactions have been reversed and will not be included on the main chain. The Litecoin team stated that all valid transactions during this period remained unaffected.

Litecoin update: • A zero-day vulnerability triggered a denial-of-service attack, causing major mining pools to go offline. • Unupdated mining nodes allow invalid MWEB transactions, enabling them to anchor tokens to third-party DEXs. • A reorganization involving 13 blocks reversed those invalid transactions—they will no longer appear...

The vulnerability has been fully patched. The Litecoin network continues to operate normally. A new core version with important security updates has since been released.

A 51% attack is considered a novel threat to blockchain security, especially for proof-of-work (PoW) blockchains such as Litecoin. This is because the blockchain consensus algorithm fundamentally follows the majority rule. If an attacker controls more than 50% of the hashing power of a PoW blockchain, they will be able to create new blocks faster than all other participants combined.

In August 2025, Monero experienced an unsuccessful 51% attack, during which the Qubic mining pool performed a six-block reorganization of the Monero ledger, resulting in approximately 60 blocks becoming orphans.

Shortly after releasing the latest update on the incident, Litecoin officially announced the release of Core 0.21.5.4, which includes critical security updates. The official team urges all node operators and wallet users to upgrade as soon as possible.

This version addresses several critical security issues and fixes the MWEB input/output fee accounting mechanism. All node operators, miners, and wallet users must upgrade. It prevents kernel fee overflow during MWEB transaction validation and clears corrupted block data to protect miners from denial-of-service (DoS) attacks. Additionally, miners will no longer include MWEB transactions in blocks when the total sum of input and output commitments is zero.