Incident Overview
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.
Incident Report
Protocol Information
Market Context at Time of Hack
What the Attacker Needed to Succeed
Understanding the prerequisites for this type of attack helps auditors identify protocols that are most at risk and helps developers build better defenses.
What Auditors Should Check
If you're auditing a protocol with similar architecture to Astera.fi, these are the critical security checks that could have prevented this incident (October 2025).
- Verify all logic paths related to Oracle Price Feed Manipulation / Flash Loan Attack are guarded by proper access controls and input validation - see the Flash Loans Attacks attack class for patterns
- Audit oracle price feeds for manipulation risks - ensure time-weighted average prices (TWAPs) or multi-source aggregators are used, not spot prices
- Review privileged functions (owner, admin, governance) for potential abuse vectors - centralization risks should be documented and bounded with timelocks or multi-sigs
Master these auditing techniques with hands-on labs and real exploit scenarios in the Smart Contract Hacking course.
Free TrialFunds Recovery
Recovered
$440K
Net Loss
382163
Security Audit History
- Audit Report 1 Report
Related Attack Classes
The technique used in this hack maps to these vulnerability classes in our security curriculum:
Sources & References
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