Smart contracts are a fundamental component of applications built using blockchain or distributed ledger technology. These contracts consist of computer code that defines a set of rules mutually agreed upon by all involved parties. Once the predetermined conditions are met, the smart contract autonomously executes, facilitating the completion of the transaction without the need for intermediaries. Ethereum, as an open and global computing platform, enables the exchange of value, automated workflows, and the creation of general-purpose applications, utilizing smart contracts to enforce these processes. Unlike traditional software, smart contracts are immutable once deployed on the blockchain, meaning they cannot be modified or updated, even for security patches. This highlights the critical need for developers to implement strong security measures prior to deployment to prevent potential exploitation. Securing Ethereum smart contracts is vital to the overall security of the blockchain, as the open-source nature of the platform allows anyone to create and deploy contracts, including malicious ones, for personal gain. This paper conducts a critical review and comparison of key vulnerabilities in Solidity-coded smart contracts. Five major weaknesses are examined: re-entrancy attacks, integer overflow, unchecked external calls, denial of service, and gasless send. The findings reveal that several of these vulnerabilities pose significant risks, with some having high severity and moderate to high likelihood of occurrence. The paper also outlines key mitigation strategies to address these security challenges.