Smart Contract Security: The Vulnerabilities That Actually Get Projects Hacked
Most smart contract hacks trace back to a small handful of well-known vulnerability patterns. Knowing them will not make you a security auditor, but it will help you ask the right questions before you deploy.
Reentrancy
A malicious contract calls back into your function before its first execution finishes, draining funds through repeated withdrawals. The fix: update your contract’s internal state before sending funds out, not after, and use reentrancy guards on functions that transfer value.
Integer overflow and underflow
Older Solidity versions let numbers wrap silently past their maximum or minimum value, which attackers could exploit to mint fake balances. Modern Solidity (0.8 and above) reverts on overflow by default, but unchecked blocks in older code are still worth checking.
Access control gaps
Functions that should be admin-only but are missing the right modifier are one of the most common and most damaging mistakes. Every privileged function needs an explicit check on who is allowed to call it.
Oracle manipulation
DeFi contracts that rely on a price feed are only as safe as that feed. If your contract pulls a price directly from a single DEX pool, an attacker can manipulate that pool with a flash loan and trick your contract into a bad trade. A decentralized oracle network or time-weighted average price closes this gap.
Unchecked external calls
Any time your contract calls another contract, that call can fail, behave unexpectedly, or call back into your code. Treat every external call as untrusted, check its return value, and follow the checks-effects-interactions pattern.
Before you deploy
None of this replaces a real audit. But a contract that already avoids these five patterns walks into an audit in much better shape, and costs less to review because the auditor isn’t finding the basics.
Need this built? I’m Saqarmax — I design and build secure smart contracts, tokens, and full Web3 products for startups and founders. See my blockchain & full-stack services or get in touch to talk through your project.