dhanjani/solv-protocol-exploit

solv-protocol-exploit

Exploit to buy orders on solv such that the seller gets 0 because the amount is sent to the 0x0 address.

Vulnerability Disclosure

Reported to solv by multiple researchers.

Fixed by solv: https://etherscan.io/tx/0xc6002001c0c38045401a2e5627e314941f20824f807ddfd7a0dc783133d743fa

The Vulnerability

1. An attacker can buy in item for all but 1 available units using buyBuyUnits(..).
2. _buy() invokes doTransferOut which if transferring to a contract calls onVNFTReceived on the receiving end.
3. Now the onVNFTReceived callback can invoke_buy() again via buyByAmount(..) or buyByUnits(..) and buy the remaining 1 unit in the item.
4. This will cause _buy() to cancel the order :

delete sales[sale_.saleId];

5. This sets sales[sale_.saleId] to 0x.
6. The seller is paid 0 for the 1 unit (too small) and the rest of the payment goes to the 0x address.