Grim Finance (2021) — Crypto Hack
LaunderedGrim Finance vaults on Fantom were exploited via a reentrancy attack, with the attacker inserting malicious tokens into the deposit flow.
Summary
Grim Finance vaults on Fantom were exploited via a reentrancy attack, with the attacker inserting malicious tokens into the deposit flow.
How It Was Compromised — DeFi via Reentrancy
The attacker exploited a reentrancy vulnerability in Grim Finance's vault contracts. When depositing LP tokens, the vault called an external contract (the LP token contract) before updating internal state. By creating a malicious token that triggered a reentrant deposit call on each transfer, the attacker could deposit the same funds multiple times, receiving vastly inflated vault shares.
Fund Flow & Laundering Analysis
Stolen funds converted to stablecoins via SpookySwap and other Fantom DEXes. Funds bridged from Fantom to Ethereum via Anyswap and routed through Tornado Cash. Grim Finance paused all vaults and published a post-mortem. The protocol was audited but the reentrancy vector was missed. No attacker identified, no recovery.