Oracle Manipulation

Oracle Manipulation Playbook

DeFi protocols that read a price from an on-chain source are vulnerable when the source can be moved within a single transaction or block. Classic vectors:

1. Spot-price AMM oracle — reserve1 / reserve0 of a Uniswap V2 pool. Anyone with enough capital (or a flash loan) can push the price for one block.
2. Manipulable TWAP — short window TWAP, or TWAP over a low-liquidity pool.
3. Single Chainlink feed without staleness check — feed returns 0 / stale → uses 0 in math.
4. Custom oracle reading from manipulable storage — e.g., a "fair-price" oracle that reads totalSupply() of an LP token alongside reserves.
5. L2 sequencer offline — L2 oracles need a "is sequencer up?" check or attacker can exploit when sequencer downs and feeds freeze.

Audit steps

1. Locate price-reading code

# Common patterns
grep -rn 'getReserves\|getAmountsOut\|getPriceFromSqrtPriceX96\|latestAnswer\|latestRoundData' src/

# Custom oracle reads
grep -rn 'IPriceOracle\|getPrice\|consult' src/

2. Trace each price use

For each call:

• Is the price read from a Uniswap V2 / Sushi / Camelot pool's reserves? → spot price = manipulable
• Is the price read from a Uniswap V3 pool's slot0.sqrtPriceX96? → manipulable
• Is it a Uniswap V3 TWAP via OracleLibrary.consult? → check the secondsAgo window (>= 1800s = 30 min is the safe minimum)
• Is it a Chainlink latestRoundData() call? → check: is updatedAt validated? Is answeredInRound >= roundId? Is answer > 0? Are L2 sequencer feeds checked?

3. Validate staleness handling

// MISSING — vulnerable
(, int256 price, , , ) = priceFeed.latestRoundData();

// GOOD — explicit staleness + sequencer
(uint80 roundId, int256 price, , uint256 updatedAt, uint80 answeredInRound) = priceFeed.latestRoundData();
require(price > 0, "ORACLE_NEGATIVE");
require(updatedAt > block.timestamp - MAX_DELAY, "ORACLE_STALE");
require(answeredInRound >= roundId, "ORACLE_OLD_ROUND");
// On L2: also check sequencer uptime feed (L2 SequencerUptimeFeed)

4. Trace the price's use

The bug isn't oracle-reading — it's oracle-trusting. Find where the price drives a state change:

• Liquidation thresholds
• Collateral valuation
• Borrow limits
• Swap output amounts (slippage check)
• LP token pricing for vaults

PoC via Foundry

Flash-loan price push (Uniswap V2 reserves)

// Pseudo:
contract Test_oracle is Test {
    function test_manipulate() public {
        // 1. Flash-loan WETH from Aave / Balancer / Uniswap V3
        // 2. Swap WETH → token in target pool, draining one side
        // 3. Reserves now skewed → spot price way off
        // 4. Call vulnerable protocol's price-dependent function
        //    (e.g., borrow USDC against overvalued collateral)
        // 5. Reverse the swap, repay flash loan
        // 6. Profit = whatever was extracted in step 4
        assertGt(USDC.balanceOf(attacker), 0, "should profit");
    }
}

Decepticon helper:

foundry_oracle_test(target="LendingPool", price_feed="UniV2Pair",
                    token0="WETH", token1="TARGETTOKEN", target_path="src/LendingPool.sol")

Chainlink stale check missing

function test_stale_price() public {
    // mock the feed to return updatedAt that's 24h old
    vm.mockCall(
        address(priceFeed),
        abi.encodeWithSignature("latestRoundData()"),
        abi.encode(uint80(1), int256(STALE_PRICE), uint256(0), block.timestamp - 86400, uint80(1))
    );

    // call function — should revert if staleness checked, should proceed if not
    target.priceDependentFunction();
    // If we reach here w/o revert → bug
}

Severity calibration

CVSS

• Spot-oracle + flash-loan available + drains protocol: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H = 10.0 (Crit)
• 30-min TWAP on illiquid pair: 7-8 (High)
• Missing staleness + Chainlink usually fresh: 5-6 (Medium)

Defender remediation

// Use Chainlink properly, not spot-price
function getPrice() internal view returns (uint256) {
    (uint80 roundId, int256 answer, , uint256 updatedAt, uint80 answeredInRound)
        = priceFeed.latestRoundData();
    require(answer > 0, "neg price");
    require(updatedAt > block.timestamp - 1 hours, "stale");
    require(answeredInRound >= roundId, "old round");
    // L2 only:
    (, int256 sequencerStatus, , uint256 sequencerStart, ) = sequencerFeed.latestRoundData();
    require(sequencerStatus == 0, "sequencer down");
    require(block.timestamp - sequencerStart > 1 hours, "grace period");
    return uint256(answer);
}

// Where Chainlink unavailable: use 30+ min Uniswap V3 TWAP w/ deep-liquidity pool
function getTwap(uint32 secondsAgo) internal view returns (uint160 sqrtPriceX96) {
    (int24 arithmeticMeanTick, ) = OracleLibrary.consult(pool, secondsAgo);
    return TickMath.getSqrtRatioAtTick(arithmeticMeanTick);
}

Known exemplars

• bZx Feb 2020: $645k via Synthetix sUSD spot-price oracle
• Harvest Finance Oct 2020: $24M via Curve pool spot price
• Cream Oct 2021: $130M via Yearn share-price manipulation
• Mango Markets Oct 2022: $114M via MNGO spot price on AMM
• Avraham Eisenberg's pattern, exactly: deposit small collateral, manipulate oracle, borrow against inflated value
• Inverse Finance Apr 2022: $15M via INV/ETH spot price
• Beanstalk Apr 2022: $182M via governance + flash-loan oracle (different but related)