The Open Web Application Security Project (OWASP) publishes the OWASP Smart Contract Top 10.

The Open Web Application Security Project (OWASP) is a reference document outlining the 10 most critical vulnerabilities in blockchain smart contracts based on attack trends and real-world data from 2025.

 This report focuses on smart contracts used in Web3, DeFi, NFTs, and other decentralized applications.

A smart contract is a program that operates automatically without intermediaries to manage money or business rules. However, if it contains errors, an attacker can steal funds or alter its behavior.

The ten most critical vulnerabilities identified by OWASP are:

1. Access Control Vulnerabilities
Allows unauthorized users to execute sensitive functions or take control of the contract.

2. Business Logic Vulnerabilities
Flaws in the protocol logic design that allow the exploitation of economic rules (e.g., how rewards are calculated). 

3. Price Oracle Manipulation
When the contract relies on external prices that can be falsified or manipulated.

4. Flash Loan-Facilitated Attacks
Use of instant, unsecured loans to magnify small vulnerabilities into large losses.

5. Lack of Input Validation
The contract does not properly verify incoming data, which can corrupt its operation.

6. Unchecked External Calls
The contract interacts with other contracts or addresses without securely handling errors or rollbacks.

7. Arithmetic Errors
Integer math errors that can be exploited to create imbalances in values.

8. Reentry Attacks
A classic vulnerability where external calls allow re-entry into a function before it completes, potentially draining funds. 

9. Integer Overflow and Underflow
When arithmetic operations exceed the allowed range and cause incorrect results.

10. Proxy & Upgradeability Vulnerabilities
Problems in how contracts are updated or replaced, allowing attackers to take control or corrupt state.

This document attempts to anticipate which types of vulnerabilities will be most relevant in 2026, based on previous incidents and expert surveys.

 It also helps raise awareness of the most dangerous flaws, prevent attacks by designing secure contracts, and assist in auditing and improving contract quality before deployment.