Oracle Failure
When the outside data a blockchain application depends on, usually a price, is wrong, delayed, or manipulated, and the application acts on it anyway.
Blockchains cannot see outside themselves, so lending protocols, derivatives, and stablecoins import prices through oracles. If an oracle reads a single venue or a thin liquidity pool, an attacker can move that price temporarily, often with borrowed funds repaid in the same transaction through a flash loan, and then borrow against collateral the protocol now overvalues or trigger liquidations that should not occur. Failures also come from staleness, where a feed stops updating during volatility, and from mismatched decimals or an incorrect asset mapping in configuration. Mitigations include aggregating many independent sources, time-weighted averages that are expensive to move, deviation thresholds, heartbeat checks, and circuit breakers that pause a market when the feed looks implausible.
Na prática
A lending market that prices collateral from one automated market maker pool can be attacked by pushing that pool's price with a large temporary trade, borrowing against the inflated valuation, and leaving the debt behind.
O equívoco comum
That an oracle failure means the blockchain was hacked, when the chain executed exactly as written and the fault was in the data it was given.