Incident All ledgers
MonoX: $31.4m
MonoX lost $31.4m on 30 November 2021. Ranked 96th of 1,272 crypto failures, with method, returned funds and comparable incidents.
- Date
- 30 November 2021
- Lost
- $31.4m
- Returned or repaid
- None recorded
- Target
- DeFi Protocol
- Category
- Protocol Logic
- Method
- Swap Logic Flaw
- Chains
- Ethereum, Polygon
On November 30, 2021, an attacker drained about $31.4 million from MonoX on Ethereum and Polygon by abusing a swap function that permitted swapping a token for itself, repeatedly inflating the MONO price to extract WETH and MATIC.
Against the ledger
- It ranks 96th of the 1,272 incidents with a known loss, and 20th in 2021.
- It accounts for 26.3% of the $119.3m in known losses in November 2021.
- 164 incidents in the ledger are classified as Protocol Logic, for $293.4m in total. This one is 10.7% of that.
- The ledger records no returned funds.
Closest in size by the same method
| Date | Target | Lost | Type | Method | Returned |
|---|---|---|---|---|---|
| 02 Nov 2026 | Mercado Bitcoin | $40.0m | CEX | Protocol Logic | — |
| 13 Feb 2021 | Alpha Finance | $37.5m | DeFi Protocol | Borrow Logic Flaw | — |
| 03 Aug 2021 | Popsicle Finance | $20.7m | DeFi Protocol | Reward Logic Flaw | — |
| 17 May 2021 | BearnFi | $18.0m | DeFi Protocol | Withdrawal Logic Flaw | — |
| 25 Mar 2025 | Abracadabra Spell | $13.0m | DeFi Protocol | Liquidation Logic Flaw | — |
All failures in 2021 · The failures ledger
Amounts are DefiLlama’s estimates and can change as incidents are revalued. Its returned figure can include money a company repaid itself, not only funds recovered from attackers. Source: DefiLlama.
Cite this Bitminer.io, “MonoX, failures ledger”, data to 2 November 2026, https://bitminer.io/ledger/incident/monox-2021-11-30/. How this is built