Thetanuts Finance Exploited as Legacy Vault Flaw Leads to $2.1 Million Incident

Thetanuts Finance suffered an exploit on Ethereum on June 15, 2026, after an attacker abused a flaw in a legacy index vault contract, according to blockchain security firms Blockaid, ExVul, and PeckShield.

Blockaid was the first to report the incident, writing on X that its exploit detection system identified an ongoing attack targeting a Thetanuts Finance index token vault. The security firm linked the incident to a low-supply accounting flaw that allowed the attacker to manipulate minting and redemption calculations.

According to Blockaid, the attacker used a flash loan to reduce the token supply to a near-zero level before reminting tokens at a heavily discounted rate due to rounding behavior in the contract's math. The firm initially estimated losses at around $105,500 in USDC.

ExVul later published a technical analysis of the exploit and described the affected product as a legacy index vault. The security firm said the vault used a redemption formula that became vulnerable when token supply was reduced to an extremely low level.

According to ExVul, the attacker was able to trigger inflated redemption values and repeatedly cycle through mint-and-claim transactions to withdraw more underlying assets than were deposited. The attack was amplified using flash-loaned capital.

Shortly after the initial reports, PeckShield published a significantly higher estimate of the incident's impact. The blockchain security company said Thetanuts Finance had been exploited for $2.1 million and added that around $2 million worth of option tokens appeared to have been secured by whitehat actors.

PeckShield also reported that the exploiter converted roughly $105,000 in USDC into ETH and continued to hold additional assets linked to the attack.

In a statement posted on X, Thetanuts Finance said its preliminary investigation indicated that the exploited vault was "once again, a deprecated vault that we have migrated from years ago." The team added that the affected vault had "no relation to any of our current contracts or products" and said a post-mortem would be released after further investigation.

What Is Thetanuts Finance?

Thetanuts Finance is a decentralized finance protocol focused on crypto options and structured products. The platform was launched to provide users with automated strategies that generate yield through options trading without requiring advanced derivatives knowledge.

Over the years, Thetanuts expanded its product suite to include options vaults, structured products, and index-based investment strategies across multiple blockchain networks. The protocol is part of a broader category of DeFi projects that use derivatives and automated vaults to offer alternative yield opportunities beyond traditional lending and staking.