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Onyx Protocol Price/Interest Exploit

  • Project: Onyx Protocol
  • Exploit_type: Flash Loan Price Manipulation + Rounding Bug (Compound v2 fork)
  • Loss: ~$3.8 million
  • Entry_point: Mint/Redeem functions in new VUSD and Lending Markets
  • Exploit_vector: The attacker leveraged flash loans to mint/redeem via empty VUSD markets, triggering exchange rate errors, combined with NFT liquidation misvalidation to extract funds.
  • Severity: Critical
  • Attack_steps:
    • Created an empty VUSD market without initial liquidity, then donated tokens to seed it.
    • Used flash loans to mint large VUSD through this low-liquidity market, exploiting rounding errors in market exchange rates.
    • Redeemed VUSD for underlying assets at manipulated rates, draining funds.
    • Took advantage of improper validation in NFTLiquidation contract to increase liquidation rewards, compounding extraction.
  • Impact: Protocol drained of ~4.1M VUSD, 7.35M XCN, 0.23 WBTC, 5 k DAI, 50 k USDT; ~$3.8M total
  • Exploitability: High
  • Root_cause: Inherited rounding error in Compound v2 fork under low-liquidity conditions and flawed input validation in liquidation contract
  • Resource:Link