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Balancer tells legacy V1 liquidity providers to withdraw after drain bug
Blockchain security firm SlowMist estimated one affected Balancer V1 pool lost about $234,000, citing a fixed-point rounding flaw exploited to drain multiple tokens.
Balancer has told liquidity providers to exit its legacy V1 pools after the protocol said it was aware of a bug that could allow LP funds to be drained. In a notice dated Aug. 31, the protocol said the deprecated pools are non-pausable, so users must act directly rather than relying on a protocol pause.
Balancer directed LPs who still hold positions in the old contracts to withdraw proportionally through its legacy withdrawal interface. It said its other products are not affected, and it did not provide an estimate of how much value remains in the impacted pools or publish the pool addresses.
Blockchain security firm SlowMist separately estimated that one Balancer V1 pool lost roughly $234,000. SlowMist attributed the drain to fixed-point rounding in the joinswapPoolAmountOut path, saying the attacker compressed the pool’s WBTC reserve to dust so the calculation rounded the required input down to one satoshi of WBTC while still minting the requested pool tokens.
SlowMist said the attacker then exited those pool tokens proportionally to drain DPI, USDC, WETH, and WBTC from the pool. Balancer’s documentation for its exit tool says it scans positions against a bundled pool list and supports proportional exits from V1 core and smart pools, with an option to add a pool manually by pasting its address if it is missing from the scan.