Summary

The current implementation of the approve function in the VaultRouterBranch.sol contract overwrites the existing allowance instead of increasing it. This can lead to potential issues when multiple transactions are performed in quick succession, causing the allowance to be reset and potentially blocking further transactions.

Vulnerability Details

The issue is located in the following code snippet:

The approve function is used to set the allowance for the vault to transfer tokens. However, instead of increasing the existing allowance, it overwrites it with the new value. This can cause issues if there are pending transactions that rely on the previous allowance.

Impact

The impact of this issue is that it can block further transactions if the allowance is reset while there are pending transactions. This can lead to a denial of service for users attempting to perform multiple transactions in quick succession.

Tools Used

• Manual code review

Recommendations

To mitigate this issue, it is recommended to use the increaseAllowance function instead of approve to ensure that the existing allowance is increased rather than overwritten. This can be achieved by implementing the following changes:

1. Use the increaseAllowance function to increase the existing allowance.