Smart Contract Vulnerabilities: Common Flaws and How to Avoid Them
When you interact with a smart contract, a self-executing program on a blockchain that runs exactly as coded without human intervention. Also known as on-chain logic, it’s meant to be trustless—but if it’s poorly written, it becomes a target. Thousands of dollars have vanished because a single line of code had a flaw no one noticed until it was too late. This isn’t science fiction. In 2022, one bug in a DeFi protocol drained over $600 million. The problem isn’t the blockchain—it’s the code built on top of it.
Smart contract vulnerabilities aren’t about weak passwords or stolen keys. They’re about logic errors: reentrancy attacks where a contract calls itself repeatedly, overflow bugs that let someone mint infinite tokens, or access control mistakes that let anyone freeze funds. These aren’t theoretical risks. They’ve happened. The DAO hack in 2016, Parity wallet freezes in 2017, and the recent Ronin Bridge breach all came down to code that looked fine to the developer but had hidden traps. Ethereum smart contracts, the most common type of smart contract, built on the Ethereum Virtual Machine are especially exposed because they’re used for high-value transactions and are open for anyone to inspect—making them both transparent and tempting.
Fixing these flaws isn’t about hiring a genius coder. It’s about process. Smart contract audits, independent reviews by security experts who test code under real attack conditions catch 80% of known issues before deployment. Tools like Slither and MythX scan for patterns linked to past exploits, but no tool replaces a human auditor who understands how attackers think. Even then, audits aren’t foolproof. The best defense is simplicity: write less code, avoid complex logic, and test every edge case. Don’t assume your code is secure just because it compiles. If it handles money, treat it like a vault with a broken lock.
What you’ll find below isn’t theory. It’s real cases. Posts here break down how hackers found gaps in popular protocols, what the code looked like before and after the fix, and how businesses are building smarter contracts today. You’ll see how small teams avoid common traps, how audits are done in practice, and why some projects never recover—even when they patch the bug. This isn’t about fear. It’s about awareness. If you’re using, building, or investing in blockchain applications, you need to understand what can go wrong—and how to stop it before it happens.
