Major cryptocurrency exchanges are publicly disclosing how much of their customers' assets they hold in offline cold storage, following last week's $6.36 billion attack on Binance's internet-connected hot wallets — the largest cryptocurrency exploit on record. Disclosures published in the days since the breach include figures from Coinbase, Gate, Upbit, OKX and several South Korean platforms.

Coinbase and Gate Publish Storage Figures

Coinbase disclosed that more than 99% of customer assets are held in cold storage, with excess assets continuously transferred offline.

Gate reported that 88.26% of its total assets are held in cold wallets, while the remaining 11.74% are maintained in hot wallets. The exchange's newly introduced Proof of Security framework indicates that its cold storage could cover 104.58% of customer assets even if its hot wallets were completely drained. These figures are undergoing independent third-party review, a process that subjects Gate's self-published security metrics to external verification.

Cold storage refers to wallets kept offline and beyond the reach of internet-based attackers, while hot wallets, which maintain an internet connection, allow exchanges to process deposits and withdrawals in real time. Because hot wallets are reachable online by design, they represent the portion of reserves most exposed to attackers — the component targeted in the Binance exploit. The split between the two has long been treated as a rough indicator of an exchange's operational security, though the Binance breach has prompted closer scrutiny of what these figures actually reveal.

South Korean Platforms Report Storage Ratios

Upbit reported that 99.17% of its assets were held in cold storage as of September 2026, leaving 0.83% in hot wallets. Its parent company, Dunamu, said the ratio was the highest among South Korea's five major cryptocurrency exchanges and exceeded the regulatory minimum of 80%.

Other South Korean exchanges reported lower cold storage ratios:

• Bithumb: 94.76%
• Coinone: 85%
• Digital X (formerly Korbit): 82.79%
• GOPAX: 80.54%

Each of the four reported figures above the 80% regulatory minimum cited by Dunamu.

Elsewhere, OKX's security disclosure, last updated on September 18, 2026, showed that more than 95% of customer crypto assets were held in cold wallets, with less than 5% in hot wallets.

Binance has not disclosed an exact breakdown of its own asset storage arrangements. Chief Executive Richard Teng has said the vast majority of customer assets are held in cold wallets — a level of detail that stops short of the specific ratios now published by its peers.

Most of the $6.36 Billion Stolen Within About 20 Minutes

According to blockchain intelligence firm TRM Labs, the attack targeted Binance's hot-wallet infrastructure and resulted in approximately $6.36 billion in stolen assets, with most of the theft occurring within about 20 minutes.

The incident has renewed questions about how exchanges manage the balance between keeping customer assets accessible for withdrawals and protecting reserves against internet-based attacks — a trade-off that each of the newly published ratios quantifies differently.

Cold Storage Ratios Have Limits

Cold storage ratios alone do not provide a complete picture of exchange security. Offline wallets can also be exposed through compromised signing systems, inadequate access controls, or employees approving fraudulent transactions.

Hong Kong's Securities and Futures Commission warned in an August 2025 circular that weaknesses in these systems could compromise both hot- and cold-wallet infrastructure.

The newly published disclosures also require careful comparison, as exchanges use different reporting periods and may calculate their cold storage ratios against different asset bases. For readers tracking how this develops, the near-term markers are the outcome of Gate's independent review and whether Binance publishes an exact storage breakdown of its own.

Source: BitcoinKE