Crypto Exchange Hack Drains $46M as Binance Deploys Bitcoin Reserves

Mercado Bitcoin halted deposits and withdrawals after a security incident reportedly drained more than $46 million from the Brazilian cryptocurrency exchange’s wallets. According to Certik senior security engineer Dickson Wu, the attackers targeted eight small blockchain networks—including Base, Optimism and Arbitrum—for roughly four hours before reaching the exchange’s main hot wallets. Addresses tied to the incident continued receiving funds for several hours after the suspension was announced.

The attack was conducted through standard transfers rather than a smart-contract exploit. Wu said the attackers transferred small amounts of Ether from 27,160 addresses, potentially allowing them to move funds held in Mercado Bitcoin customer deposit addresses. The exchange said customers had not suffered losses and that no data was leaked, although the incident could trigger notification requirements involving Brazil’s data protection authority. No organized group has been publicly identified, and the investigation remains ongoing.

Binance also drew on its emergency reserves following Thursday’s reported $6.3 billion attack, which the FBI attributed to North Korea. The exchange transferred 7,499 BTC into its publicly disclosed emergency wallet on Saturday, partially deploying its Secure Asset Fund for Users, or SAFU. By Monday, the wallet held approximately 7,500 BTC worth about $583 million, down from roughly 15,000 BTC before the transfer.

Binance began reopening withdrawals in phases on Sunday and said it had replenished about 95% of the affected assets, up from 90% the previous day. It also continued purchasing remaining, less-liquid tokens through market and over-the-counter transactions. Together, the Mercado Bitcoin theft and Binance’s reserve deployment highlight the risks facing centralized exchanges as attackers target hot wallets and customer deposits.