What happened
On November 30, 2025, an attacker exploited the Ethereum yETH weighted stableswap pool, draining about $9 million. The attacker forced the pool's invariant solver into a divergent state, over-minted yETH LP tokens, drained the pool's liquid-staking assets, and then used the empty-pool initialization path to mint an enormous additional yETH supply with dust deposits. Yearn says the impact was confined to yETH and direct integrators; recovery efforts recovered 857.49 pxETH and remained ongoing.
How it happened
- The attacker used extremely imbalanced liquidity additions to force the stableswap solver into a divergent state and over-mint yETH LP tokens.
- They used those tokens in repeated withdrawals to drain liquid-staking assets and reduce the pool's internal supply to zero.
- They re-entered the initialization path with dust deposits after the pool was empty.
- An arithmetic underflow minted approximately 2.3544 × 10⁵⁶ yETH LP tokens, which were used to drain the yETH/ETH Curve pool.
Protocol details
Security review history
- ChainSecurity View report
- MixBytes View report
- Quantstamp View report
- PeckShield View report
Evidence
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