How Secure Are Smart Contracts: A History of Vulnerabilities and Attacks?

Historical overview of major smart contract vulnerabilities since 2016

Since 2016, smart contract vulnerabilities have evolved significantly, presenting various challenges to blockchain security. The reentrancy attack, which led to the infamous DAO hack in 2016, remained a critical concern through 2017. This exploit allowed attackers to drain over 3.6 million Ether from the Decentralized Autonomous Organization. As the industry progressed, new vulnerabilities emerged. From 2020 onwards, integer overflow/underflow and access control issues became increasingly prominent. The following table illustrates the shift in major vulnerabilities over time:

| Year Range | Primary Vulnerabilities | |------------|-------------------------| | 2016-2017 | Reentrancy Attacks | | 2018-2019 | Default Visibilities | | 2020-2022 | Integer Overflow/Underflow, Access Control | | 2023-2025 | Flash Loan Attacks, Price Oracle Manipulation |

Recent developments have seen a rise in sophisticated exploits such as flash loan attacks and price oracle manipulation. These vulnerabilities have led to significant financial losses, underscoring the critical need for robust security measures in smart contract development and auditing. The evolving nature of these vulnerabilities highlights the importance of continuous security updates and proactive risk management in the blockchain ecosystem.

Analysis of 5 notable cyberattacks on blockchain networks

In 2025, the blockchain industry witnessed several significant cyberattacks that exposed vulnerabilities and had far-reaching consequences. The WEMIX blockchain gaming platform fell victim to a breach resulting in the theft of 8.65 million WEMIX tokens, valued at approximately $6.1 million. The attackers exploited stolen authentication keys tied to the platform's NFT service, highlighting the importance of secure key management. NTT Communications experienced a major data breach affecting nearly 18,000 corporate clients, compromising sensitive information including company names, contract numbers, and email addresses. This incident underscored the risks associated with third-party service providers and the need for robust supply chain security measures.

| Attack | Target | Impact | |--------|--------|--------| | WEMIX Breach | Blockchain gaming platform | $6.1 million stolen | | NTT Communications Breach | Corporate data | 18,000 clients affected | | Harrods Data Exposure | Luxury retailer | 430,000 customer records exposed |

The Harrods data breach exposed approximately 430,000 customer records due to a supply chain attack, emphasizing the vulnerability of even prestigious institutions to cybercriminals targeting the retail sector. These incidents collectively demonstrate the evolving threat landscape in the blockchain and corporate sectors, necessitating enhanced security protocols, improved incident response mechanisms, and a renewed focus on protecting sensitive data across interconnected systems.

Centralized exchange risks: Case studies of Mt. Gox and QuadrigaCX

The collapse of Mt. Gox in 2014 and QuadrigaCX in 2019 exposed significant vulnerabilities in centralized cryptocurrency exchanges. These high-profile cases highlight the inherent risks associated with entrusting digital assets to third-party custodians. Mt. Gox, once handling 70% of global Bitcoin transactions, lost approximately 850,000 BTC due to alleged hacking and mismanagement. Similarly, QuadrigaCX's insolvency resulted in the loss of $190 million in user funds, attributed to the unexpected death of its CEO and subsequent inaccessibility of cold wallets. A comparison of these incidents reveals common risk factors:

| Risk Factor | Mt. Gox | QuadrigaCX | |-------------|---------|------------| | Security Breach | ✓ | ✗ | | Mismanagement | ✓ | ✓ | | Lack of Transparency | ✓ | ✓ | | Single Point of Failure | ✓ | ✓ |

These cases underscore the importance of implementing robust security measures, transparent operations, and decentralized control mechanisms in cryptocurrency exchanges. The industry has since witnessed the rise of decentralized finance (DeFi) platforms as a response to these centralized exchange failures, offering alternative solutions that aim to mitigate risks through smart contracts and distributed governance models.