1/ @fi_dynamic $DYNA on #BSC was hacked (bscscan.com/tx/0xc09678fec…) and the loss is ~73 BNB.
The root cause is that the StakingDYNA contract (bscscan.com/address/0xa7B5…) does not handle the deposit time correctly.
The root cause is that the StakingDYNA contract (bscscan.com/address/0xa7B5…) does not handle the deposit time correctly.
https://twitter.com/MetaSleuth/status/1628310811579150337
2/ Specifically, users could deposit $DYNA and claim rewards, while the interest will be calculated as follows:
duration = now - lastProcessAt
interest = k * (stakeAmount * duration)
However, the user's lastProcessAt is only recorded for the first deposit/stake.
duration = now - lastProcessAt
interest = k * (stakeAmount * duration)
However, the user's lastProcessAt is only recorded for the first deposit/stake.
3/ Thus, attackers could: 1) open a new vault and deposit a few $DYNA at time A; 2) after a while (at time B), borrow a large amount of $DYNA by flashloan and deposit them; 3) redeem the deposit, the profit is calculated as k * (borrowAmount * (B - A)); 4) repay the flashloan.
4/ Note that steps 2, 3, and 4 are in the same tx.
In fact, the real deposit time should be 0 instead of (B - A), but the vulnerable contract does not update lastProcessAt for any deposit. Thus, the staking duration is calculated mistakenly.
In fact, the real deposit time should be 0 instead of (B - A), but the vulnerable contract does not update lastProcessAt for any deposit. Thus, the staking duration is calculated mistakenly.
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