Oracle manipulation detection

When this applies

Any code that consumes a price feed or derives a price from on-chain state:

• Chainlink: latestAnswer, latestRoundData, getRoundData
• Uniswap V2: getReserves, getAmountsOut, price0Average
• Uniswap V3/V4: slot0, observe, consult
• Curve: get_virtual_price, get_dy
• Balancer: getRate
• Custom oracle modules, on-chain TWAPs
• LP token pricing, collateral valuation, liquidation thresholds, mint/burn rates

Detection patterns

Spot price from AMM (CRITICAL — funds at risk)

(uint112 r0, uint112 r1,) = pair.getReserves();
uint256 price = r1 * 1e18 / r0;       // ← flash-loan manipulable in one block

Stale Chainlink data (HIGH)

(, int256 answer,,,) = feed.latestRoundData();   // ← ignores updatedAt and answeredInRound

Required checks:

• updatedAt != 0
• block.timestamp - updatedAt <= heartbeat (with chain-specific tolerance)
• answeredInRound >= roundId
• answer > 0
• Heartbeat sanity: ETH/USD is 1h on mainnet but 24h on some L2s — verify

latestAnswer (deprecated, no freshness) (HIGH)

int256 p = feed.latestAnswer();   // ← deprecated, prefer latestRoundData

Single-source dependence (HIGH)

Only one oracle, no fallback, no cross-check against a second source.

Uniswap V3 slot0 without TWAP (CRITICAL)

(uint160 sqrtPriceX96,,,,,,) = pool.slot0();   // ← spot, manipulable

Use observe() for TWAP with sufficient lookback (≥30min for shallow pools).

Insufficient TWAP window (HIGH)

TWAP < 5 min on volatile assets or low-liquidity pools is gameable across two blocks.

Read-only reentrancy on oracle (HIGH)

Reading getVirtualPrice / getReserves mid-callback — see [[reentrancy]] §Read-only.

LP token priced via reserves directly (CRITICAL)

LP token price should use the fair LP price formula (Alpha Homora's method), not reserve / totalSupply.

Price scaling errors (HIGH)

Chainlink answers come in feed-specific decimals; mixing ETH/USD (8 decimals) with token (18 decimals) without normalizing produces silent off-by-1e10 errors.

Sequencer uptime ignored (HIGH on L2s)

On Arbitrum, Optimism, Base — must check SequencerUptimeFeed to avoid stale prices when sequencer is down.

Severity rubric

Remediation patterns

• For Chainlink: validate (roundId, answer, , updatedAt, answeredInRound) — guard against stale + zero + non-positive + round-mismatch.
• Use multiple oracles with deviation check (e.g. Chainlink + Uniswap V3 TWAP with ≥30min window).
• For LP tokens, use fair-LP-price math: 2 * sqrt(r0 * r1 * p0 * p1) / totalSupply.
• On L2s, integrate Chainlink's SequencerUptimeFeed (Arbitrum, Optimism, Base).
• Avoid slot0 and spot-price reads for anything that affects user funds.

False-positive notes

• Display-only prices (UI/event metadata, not affecting fund flow) — Info-only.
• getReserves used purely for ratio diagnostics with no downstream effect — Info.

Related

• [[flash-loan-attacks]] — most oracle attacks are funded by flash loans
• [[reentrancy]] — read-only reentrancy is an oracle-staleness issue
• [[mev-frontrunning]] — TWAP-window timing