Hack history / 2021 / Hack or exploit
NowSwap
Hack or exploit on Sep 14, 2021 · Arithmetic Error
SOURCES AGREE ON DATE AND LOSS · 3 SOURCES
Lost
$1.1M
sources: $1M to $1.1M
Returned
none listed
as the sources state it
Rank
#904
among thefts by dollars lost
What happened
NowSwap DEX on Ethereum was exploited on September 15, 2021 when K constant value mismatch (updated in 2 of 3 code locations during upgrade) allowed attacker to swap 1 wei for 98% of pool reserves.
Details
- Date
- Sep 14, 2021
- Kind
- Hack or exploit
- Method
- Arithmetic Error
- How in
- Smart contract bug
- Target
- DeFi protocol
- Chains
- Ethereum
Reported by
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Pizza DeFi 2021 · Hack or exploit · $5M
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Cite this page
SwanBluechip, "NowSwap hack, Sep 14, 2021: $1.1M lost", Crypto hack history, https://swan-hack-tracker.pages.dev/history/i/htb34094db8a/ (data as of 2026-11-01).