🚀 Top 10 Smart Contract Vulnerabilities in Startups 📉

The rise of decentralized apps has made smart contracts more critical than ever. Yet, many startups inadvertently introduce vulnerabilities. Here are 10 common pitfalls:

1. Reentrancy:
   • Exploit: External calls can run arbitrary code, allowing repeated withdrawals.
   • Prevent: Use the checks-effects-interactions pattern.
2. Arithmetic Over/Underflows:
   • Exploit: Unsafely incrementing/decrementing can reset a variable.
   • Prevent: Use safe math libraries.
3. Unchecked Return Values:
   • Exploit: Ignored outputs may lead to unhandled exceptions.
   • Prevent: Always handle external call outcomes.
4. Timestamp Dependence:
   • Exploit: Miners can manipulate timestamps.
   • Prevent: Avoid critical operations based on block timestamp.
5. Access Control:
   • Exploit: Insufficient restrictions give attackers permissions.
   • Prevent: Properly set & frequently audit contract permissions.
6. Outdated Compiler:
   • Exploit: Old compilers may have known vulnerabilities.
   • Prevent: Regularly update and check compiler versions.
7. Immutable Bugs:
   • Exploit: Once deployed, contracts can’t be altered.
   • Prevent: Implement upgrade patterns and thorough testing.
8. Short Address Attack:
   • Exploit: Manipulate msg.data length to cause errors.
   • Prevent: Always validate the length of msg.data.
9. Uninitialized Storage Pointers:
   • Exploit: Uninitialized state variables can be overwritten.
   • Prevent: Always initialize state variables.
10. Denial of Service (DoS):

• Exploit: Flood contract, making it unusable.
• Prevent: Implement gas usage limits and anti-spam measures.

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Reentrancy:

• Vulnerable:solidity

function withdraw() public { uint amount = balances[msg.sender]; require(msg.sender.call.value(amount)()); balances[msg.sender] = 0; } Hardened:

solidity

• function withdraw() public { uint amount = balances[msg.sender]; balances[msg.sender] = 0; require(msg.sender.call.value(amount)()); }

Arithmetic Over/Underflows:

• Vulnerable:solidity

balances[msg.sender] += msg.value; Hardened (Using OpenZeppelin’s SafeMath):

solidity

• balances[msg.sender] = balances[msg.sender].add(msg.value);

Unchecked Return Values:

• Vulnerable:solidity

otherContract.execute(); Hardened:

solidity

• require(otherContract.execute());

Timestamp Dependence:

• Vulnerable:solidity

if (now >= deadline) {...} Hardened (Avoid reliance):

solidity

• // Use block number or other reliable mechanisms

Access Control:

• Vulnerable:solidity

function setOwner(address _newOwner) public { owner = _newOwner; } Hardened:

solidity

• function setOwner(address _newOwner) public onlyOwner { owner = _newOwner; }

• Vulnerable: // Allowing unbounded loop iterations or gas consumption
• Hardened: // Implementing gas checks or breaking up operations