Summary

Potential Denial of Service (DoS) vulnerability in the expel function of the LevelOne smart contract due to unbounded linear iteration through the listOfStudents array.

Vulnerability Details

The expel(address _student) function in the LevelOne contract iterates through the listOfStudents array to locate the student to be expelled. As the number of enrolled students grows, the gas cost of this operation increases linearly with the size of the array. A legitimate call by the principal to expel a student could potentially cause the transaction to exceed the block gas limit if listOfStudents becomes sufficiently large, making the expel function unusable. While the isStudent mapping allows for constant-time checks of a student's enrollment status, the array iteration for removal remains a gas bottleneck.

Impact

• Denial of Service (DoS): The expel function can become unusable for the principal if the number of students is large, preventing necessary administrative actions.

• Increased Gas Costs: Legitimate calls to expel will consume more gas than necessary, especially with a large number of students.

Tools Used

• Manual code review and analysis.

Recommendations

You can perform the look up in batches. where you specify a range of students to look at during a single call