Crypto15 July, 20262 min read
Ostium Halts Trading After Oracle Exploit Drains Nearly $18 Million USDC
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Ostium suffered an oracle exploit draining about $18 million USDC. Attackers used a compromised oracle signer key to submit fake price reports.
Oracle exploit drains Ostium
Ostium halted trading after an oracle exploit drained nearly $18 million USDC from its liquidity vault, according to blockchain security firm Blockaid. Blockaid said the attacker gained control of an oracle signer private key, allowing them to bypass the protocol’s verification process and submit future-dated price reports that favored their trades.
The incident depleted nearly one-third of the protocol’s $63 million total value locked at the time of the attack, and Blockaid said the exploit triggered around 20 trading loops that steadily drained funds from Ostium’s main vault. Ostium operates on Arbitrum and offers decentralized perpetual trading for tokenized real-world assets, including equities, commodities, foreign exchange markets and stock indices, while the primary exploit transaction can be verified on Arbiscan.
Ostium pauses, users warned
Ostium stated that it has identified issues with the OLP vault and has suspended all trading, while the team said it was investigating.
In a direct message to its user base, Ostium recommended that all users temporarily revoke approvals for its contracts until it could further investigate the recent incident: “With user security being our first concern, we recommend that all users temporarily revoke approvals for our contracts until we can further investigate the recent incident.”
Blockaid described how the attacker used a registered PriceUpKeep forwarder to repeatedly open and close positions through delegated actions, extracting profits without taking genuine market risk.
Decrypt reported that Ostium wrote on X, “We are aware of the issue with the OLP vault,” and added, “We have paused all trading. The team is investigating.”
Loss estimates and broader pattern
Loss estimates varied across reporting, with Blockaid pegging the payout at roughly $18 million while The Cryptonomist said losses ranged from $18 million to $22 million from Ostium’s OLP liquidity vault. Protos said the attacker fed self-signed favorable prices to open and immediately close trades at a profit, draining ~11.86M USDC from the OstiumVault, and it noted that Ostium’s official X account confirmed an “issue” with its OLP vault shortly thereafter.
Cointelegraph said Ostium paused trading after identifying an issue affecting the vault and that it had not yet confirmed the cause of the incident or the estimated losses reported by blockchain security firms. The attack added to a wider run of DeFi incidents, with Bitget reporting that in the first five months of 2026 DeFi protocols lost over $840 million to theft, including $292 million from KelpDAO and $285 million from Drift Protocol.