Astera.fi Hack

On October 9, 2025, Astera lending protocol on Linea was exploited for approximately $821,856 (8% of TVL) through a sophisticated liquidity index inflation attack. The attacker manipulated the USDT liquidity index from 1 to 154x using flash loan fees against a deliberately reduced supply pool, then borrowed against the artificially inflated collateral to drain three Minipools. Following the exploit, $440,000 (54%) was rescued and $380,000 (46%) was frozen by Linea's security team.

The three-phase attack exploited the protocol's Minipool unwrapping mechanism combined with flash loan fee logic. Phase 1 involved setup where the attacker supplied USDT as collateral and borrowed USDT with unwrap=true, which burned asUSDT from the Main lending pool, reducing asUSDT.totalSupply to a critical low of just 97 USDT. Phase 2 executed the core manipulation: over blocks 24321061-24321895, the attacker performed 5,600 flash loans across 112 transactions, each applying a 9 basis point fee to the extremely small asUSDT supply.

This iterative fee application massively amplified the liquidity index from 1 to 154x. Phase 3 involved draining: with collateral now overvalued 154x (making 6,000 USDT worth ~$900,000 to the oracle), the attacker borrowed nearly all available liquidity from affected Minipools, draining $442,856 in asUSD, $297,000 in LINEA, and $82,000 in WETH.

Affected Minipool Addresses:

0x52280ea8…58beb4

0x65559abe…add928

0x0bafb30b…5e3401