Core Contracts

Summary

The incorrect staking logic lead to the incorrect distribution

Vulnerability Details

• User1 deposit early (T80-T84) when the rate is higher (1.2e27 for some period).

• User2 stakes later (T83-T84) when the rate is lower (1.1 for some period).

• The contract does not properly account for these changes, leading to User1 receiving fewer rewards than expected and User2 receiving more.

(totalRewards * userDeposit) / totalDeposits

• Alice scenario

(100e18 * 50e18) / 110e18 = 45e18

(100e18 * 60e18) / 110e18 = 54e18

0.13 per 13 sec

((0.13 * 5) * 50) / 110 = 0.29 → receive Alice for 5 blocks if she stakes 50 tokens

((0.16 * 5) * 50) / 110 = 0.36 → receive Alice for 5 other blocks, with higher emission rate if she stakes 50 tokens

At the end of B90 she entitles for 0.65 reward tokens

((0.16 * 2) * 60) / 110 = 0.17 → receive Bob for 2 blocks if he stakes 60 tokens

At the end of B90 he entitles for 0.17 reward tokens

• totalRewards = 0.82

(0.82 * 50) / 110 = 0.37 → rewards receive alice upon withdrawing

(0.82 * 60) / 110 = 0.44 → rewards receive bob upon withdrawing

Block.timestamp	80	81	82	83	84
	Alice	Alice	Alice	Alice	Alice
				Bob	Bob
				Bob	Bob
				Bob	Bob

• 131944444444444444 (0.13e18) is basic emission rate upon contract deployment

• 231944444444444444 (0.23e18) is updated *PoC rate after some time.

1. Receive Alice for 2 blocks if she stakes 50e18 tokens with basic emission rate (80-82)

((131944444444444444 * 3) * 50e18) / 50e18 = 395833333333333332 (0.39e18)

1. Bob deposit 60e18 tokens more, the rate has updated. Now, from (83-84) Alice receive:

((231944444444444444 * 2) * 50e18) / 110e18 = 210858585858585858 (0.21e18)

1. Receive Bib for 2 blocks (83-84) if she stakes 60e18 tokens with updated emission rate

((231944444444444444 * 2) * 60e18) / 110e18 = 253030303030303029 (0.25e18)

totalRewards minted

1. 131944444444444444 * 3 = 395833333333333332

2. 231944444444444444 * 2 = 463888888888888888

= 859722222222222220 → 0.85e18

Upon final claiming, both Alice and Bob will receive

Alice

(859722222222222220 * 50e18) / 110e18 = 390782828282828281 (0.39e18)

Bob

(468939393939393939 * 60e18) / 60e18 = 468939393939393939 (0.46e18)

Impact

Funds loss for user

Tools Used

Manual reviwe

Recommendations

Implement correct staking logic