Hack history / 2021 / Hack or exploit
Poly Network
Hack or exploit on Aug 10, 2021 · Improper Access Control
ATTACK TX CONFIRMED ON CHAINSOURCES AGREE ON DATE AND LOSS · 5 SOURCES
Lost
$611M
dollars at the time
Returned
$611M
100% of the loss, as a source states it
Rank
#7
among thefts by dollars lost
What happened
Poly Network was exploited for $611M on August 10, 2021 across Ethereum ($273M), BSC ($253M) and Polygon ($85M) via an access control and cryptography vulnerability in cross-chain bridge contracts. The attacker voluntarily returned nearly all funds within 15 days, keeping only transaction fees.
Details
- Date
- Aug 10, 2021
- Kind
- Hack or exploit
- Method
- Improper Access Control
- How in
- Smart contract bug
- Target
- DeFi protocol
- Chains
- Ethereum, BNB Chain, Polygon
- Audit (rekt.news)
- unaudited
After the theft
- Returned by the attacker
- yes, amount not stated
“The attacker voluntarily returned nearly all funds within 15 days, keeping only transaction fees.” (DefiLlama) - Recovered or frozen
- $611M
“$611.0M taken, $0K after recovery or freezing” (Web3 Is Going Great)
Related incidents
Poly Network 2023 · Hack or exploit · $10M
Mirror 2021 · Hack or exploit · $90M
ValueDefi 2021 · Hack or exploit · $10M
DAO Maker Vesting 2021 · Hack or exploit · $7M
DAO Maker Vesting 2021 · Hack or exploit · $4M
Mirror 2021 · Hack or exploit · $90M
ValueDefi 2021 · Hack or exploit · $10M
DAO Maker Vesting 2021 · Hack or exploit · $7M
DAO Maker Vesting 2021 · Hack or exploit · $4M
Cite this page
SwanBluechip, "Poly Network hack, Aug 10, 2021: $611M lost", Crypto hack history, https://swan-hack-tracker.pages.dev/history/i/ht54839f43ad/ (data as of 2026-10-31).