Root-cause analysis not yet published. The incident description below contains all currently available signal — review the attack transaction directly for definitive forensics.
Reproducible Foundry test fork from SunWeb3Sec/DeFiHackLabs. Clone the repo, run forge test against the file path above, and replay the exploit against a mainnet fork at the historical block. Use for reproduction only — not for live targets.
Nowswap, a decentralized exchange on Ethereum, was attacked by a flash loan. The attacker emptied Nowswap’s liquidity pool. The liquidity pool was reduced from US$1,069,197 to US$24.15. The attacker made a profit of 536,000 USDT and 158 WETH. A total of more than 1 million US dollars. The attacker used the K value verification vulnerability in the Nowswap USDT/WETH transaction pair contract to perform multiple exchanges, and each exchange obtained multiple times the normal due assets, until the assets in the trading pair pool were exhausted. Attack method (per SlowMist): K value verification vulnerability. Reported loss: $ 1,000,000.
- chain
- ethereum
- protocol
- Nowswap
- bug_class
- flashloan
- date_occurred
- 2021-09-15
- loss_usd
- $1,000,000
- source_id
- sm:nowswap::2021-09-15