Ethereum liquid staking protocol Meta Pool has suffered a smart contract exploit that led to the unauthorised minting of mpETH tokens and losses exceeding $133,000.
The breach, disclosed in a June 17 blog post, was contained before more damage could occur, thanks to Meta Pool’s early detection systems and the swift intervention of blockchain security firm Blocksec. The protocol paused its mpETH contract shortly after the attack was identified, halting further exploitation.
The exploit targeted a vulnerability in the mint() function of Meta Pool’s Ethereum-based ERC-4626 staking contract. According to co-founder Claudio Cossio, the attacker appears to have leveraged the fast-unstaking mechanism to sidestep the usual unbonding process and mint mpETH without supplying any collateral.
In total, the exploiter minted 9,705 mpETH—worth nearly $27 million at the time—but was able to cash out only 52.5 ETH, valued at roughly $133,000, due to limited liquidity across swap pools. A significant portion of the losses, including 37.5 ETH, came from Meta Pool’s own liquidity on Uniswap. The attacker also drained funds from pools on the Ethereum mainnet and Layer 2 networks like Optimism.
Despite the attack, Meta Pool confirmed that user deposits—totalling 913 ETH—remain secure and are still being managed by SSV Network validators. Additionally, staking contracts on other supported chains such as NEAR, Solana, Aurora, Internet Computer, Q, and Story were not impacted by the exploit.
The Meta Pool team is working on a full post-mortem and says a recovery and reimbursement plan will be released within 48 hours. Affected users will be compensated, according to the protocol.
This incident is the second major decentralized finance (DeFi) hack reported in June. Earlier this month, Alex Protocol—a Bitcoin-based DeFi platform—lost $8.3 million after a vulnerability in its self-listing logic allowed an attacker to drain multiple asset pools. Alex Protocol has since introduced a Treasury Grant Program to compensate victims in a mix of original assets and USDC.
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