Hack history / 2021 / Hack or exploit
Siren
Hack or exploit on Sep 3, 2021 · Reentrancy
ONE SOURCE · 1 SOURCE
Lost
$3.5M
dollars at the time
Returned
none listed
as the sources state it
Rank
#554
among thefts by dollars lost
What happened
On September 3, 2021, the SIREN protocol on Polygon was exploited via reentrancy in withdrawCapital, allowing repeated withdrawals before balance updates. The attacker drained ~$3.5M across multiple AMM pools (KNC, SUSHI, USDC, WETH, WMATIC), affecting 26 LP addresses.
Details
- Date
- Sep 3, 2021
- Kind
- Hack or exploit
- Method
- Reentrancy
- How in
- Smart contract bug
- Target
- DeFi protocol
- Chains
- Polygon
Reported by
Related incidents
Grim Finance 2021 · Hack or exploit · $30M
CREAM Lending 2021 · Hack or exploit · $18.8M
flash.sx / vaults.sx 2021 · Hack or exploit · $13M
Gamma 2021 · Hack or exploit · $8.2M
BurgerSwap 2021 · Hack or exploit · $7.2M
CREAM Lending 2021 · Hack or exploit · $18.8M
flash.sx / vaults.sx 2021 · Hack or exploit · $13M
Gamma 2021 · Hack or exploit · $8.2M
BurgerSwap 2021 · Hack or exploit · $7.2M
Cite this page
SwanBluechip, "Siren hack, Sep 3, 2021: $3.5M lost", Crypto hack history, https://swan-hack-tracker.pages.dev/history/i/ht301ffca77b/ (data as of 2026-10-31).