South Korea’s largest crypto exchange, Upbit, is pushing almost all customer assets into cold storage after a major hack on its Solana hot wallet, in one of the most aggressive security pivots yet by a big trading platform.
Operator Dunamu said it will lift the share of user funds held in cold wallets to 99% and cut hot wallet exposure to effectively 0%, after hackers stole 44.5B won, about $30m, from a connected wallet.
For traders, a 99% cold ratio means a much smaller pool of funds is exposed if a hot wallet is ever compromised again. In a press statement on Wednesday, Dunamu disclosed that as of the end of Oct. 2025, Upbit held 98.33% of customer assets in cold wallets and 1.67% in hot wallets.
Cold wallets store digital assets while disconnected from the internet, making them far harder to breach but also slower to move. Hot wallets sit online to process deposits and withdrawals in real time, which makes them convenient for users but a prime target for attackers.
Upbit said it maintained its cold share above 98% despite rising crypto prices and heavier flows from new listings, and has now completed a review and overhaul of its wallet infrastructure. The company plans to drive the hot wallet ratio down to zero as it tightens its security posture.
Even before the hack, that was the lowest hot wallet share among domestic exchanges, with rivals keeping cold ratios in a range of roughly 82% to 90%, according to data released by lawmaker Heo Young.
A detailed breakdown put 38.6B won, about $26.2M, down as direct user losses, which the company has pledged to fully reimburse from its own reserves. Tokens affected in the attack included Solana’s SOL as well as ORCA, RAY and JUP, the exchange said. Once abnormal withdrawals were detected, Upbit halted activity, shifted remaining assets into cold storage and began a forensic investigation of its systems and on chain flows.
This move follows a hack worth initially about 54B won, roughly $36M, on the Solana network, which Upbit later refined to a loss estimate of 44.5B won after an internal review.
