CBSE Smart Contract Vulnerabilities 2

Question 1

Which vulnerability allows an attacker to repeatedly call a withdrawal function before the balance is updated, draining contract funds?

Accepted Answer

Reentrancy

Answer

Integer overflow

Answer

Front-running

Answer

Denial of service

Question 2

In Solidity, which pattern best mitigates reentrancy attacks by updating state before making external calls?

Accepted Answer

Checks-Effects-Interactions pattern

Answer

Oracle pattern

Answer

Pull-over-push pattern

Answer

Factory pattern

Question 3

A smart contract stores the block timestamp as a source of randomness for a lottery. What vulnerability does this introduce?

Accepted Answer

Miner manipulation of block.timestamp

Answer

Integer underflow

Answer

Access control flaw

Answer

Cross-function reentrancy

Question 4

What is a 'tx.origin' attack in Ethereum smart contracts?

Accepted Answer

Using tx.origin instead of msg.sender for authorization, which can be exploited via phishing contracts

Answer

Sending transactions with a forged origin address

Answer

Overflowing the call stack via recursive calls

Answer

Manipulating the transaction fee to bypass checks

Question 5

Which EVM feature limits the depth of nested calls, and what vulnerability arises when this limit is hit unexpectedly?

Accepted Answer

Call stack depth limit (1024) — causes unexpected call failures

Answer

Gas limit — causes out-of-gas revert

Answer

Memory limit — causes memory overflow

Answer

Storage limit — causes data truncation

Question 6

A contract uses 'delegatecall' to load logic from a library. The library's storage layout differs from the calling contract's layout. What is the risk?

Accepted Answer

Storage collision, leading to unintended state overwrites

Answer

Gas theft by the library

Answer

Permanent locking of funds in the library

Answer

Infinite loop causing denial of service

Question 7

Which vulnerability occurs when a Solidity contract performs arithmetic that silently wraps around due to type constraints in versions below 0.8.0?

Accepted Answer

Overflow/underflow

Answer

Reentrancy

Answer

Short address attack

Answer

Signature replay