Charles Guillemet, the chief technology officer at Ledger wallet, has published a tweet, in which he shared that renowned privacy blockchain-focused company Monero is undergoing a 51% attack, and this attack is successful, he believes.
He revealed the details of what is happening there and what the likely consequences might be.
51% attack hits Monero (XMR) from $300 million chain
Guillment revealed that Monero, which was launched in 2014, focused on private blockchain transactions and already banned from the majority of top centralized exchanges, has faced a 51% attack. A successful attack like this may shift the balance of mining participants, lead to a forced power grab and bring changes to the blockchain.
In particular, the Ledger CTO revealed that the Qubic mining pool has been increasing its hashrate power over the past few months. Now, it has taken the majority of the Monero network under control. This attack has succeeded, according to Guillment since, this morning, he detected a major reorganization on this chain. The CTO spoke about the potential consequences of this takeover: “With its current dominance, Qubic can rewrite the blockchain, enable double-spending, and censor any transaction.”
Monero appears to be in the midst of a successful 51% attack.The privacy-focused blockchain, launched in 2014 and long targeted by governments and 3-letters agencies, is already banned from most major centralized exchanges.The Qubic mining pool has been amassing hashrate for…
— Charles Guillemet (@P3b7_) August 12, 2025
Qubic is a separate blockchain, ranked 222nd on CoinMarketCap, with a market capitalization value of slightly under $300 million. But now, it is taking over Monero — the 30th-ranked coin. “In effect, a $300 million market-cap chain is taking over a $6 billion one,” Charles Guillemet noted.
card
Qubic likely to take over Monero: Ledger CTO
Guillemet pointed out that to sustain such an attack per day costs $75 million, adding that this attack threatens to leave the network with no confidence just overnight. Since other miners will be left with no incentives to continue supporting Monero, Qubic may remain the sole XMR miner.
It is likely that Qubic will fully take over the entire network, the Ledger CTO noted, with very limited options for Monero to recover: “Monero’s options for recovery are limited, and a full takeover is now possible and even likely.”
By now, XMR has dropped by 13%, he added.
