What Is a Cross-Chain Bridge and Why Do They Keep Getting Hacked? A Beginner’s Complete Guide

If you have spent any time in cryptocurrency, you have probably heard about cross-chain bridges. These tools let you move tokens between different blockchain networks, like sending Ethereum to Solana or moving Bitcoin to a Layer 2 network. They sound convenient, and they are, but they also happen to be the most frequently exploited part of the entire crypto ecosystem. In May 2025 alone, bridge-related exploits contributed to $244 million in total hack losses. Here is everything you need to know about how bridges work, why they get attacked, and how to protect yourself.

The Basics

A cross-chain bridge is a piece of software that connects two or more blockchains and allows them to communicate. Because blockchains like Bitcoin, Ethereum, and Solana operate independently with different rules and programming languages, they cannot natively understand each other. Bridges solve this problem by creating a pathway between networks.

Here is the most common way bridges work. When you want to move, say, 1 ETH from Ethereum to Solana, the bridge locks your 1 ETH in a smart contract on the Ethereum side. Then it mints or releases an equivalent amount of wrapped ETH on Solana. When you want to move back, the wrapped tokens get burned and your original ETH gets unlocked. The locked assets serve as collateral backing the wrapped tokens on the other chain.

With Bitcoin currently trading around $105,652 and Ethereum near $2,536, the total value locked in bridge protocols runs into billions of dollars. That massive pool of locked assets is exactly what makes bridges such attractive targets for hackers.

Why It Matters

Cross-chain bridges matter because the crypto ecosystem is increasingly multi-chain. DeFi protocols exist on Ethereum, Solana, Avalanche, BNB Chain, and dozens of other networks. Users want to move assets freely between these ecosystems without going through centralized exchanges. Bridges provide this functionality, but they introduce significant security risks in the process.

The fundamental problem is that bridges concentrate risk. When billions of dollars of assets are locked in a single bridge contract, that contract becomes one of the highest-value targets in the entire crypto space. The Force Bridge exploit in late May 2025 demonstrated this vividly when $3.9 million was drained through an access control failure. Earlier in May, the Cetus Protocol on Sui lost $220 million through a bridge-related exploit. These are not isolated incidents but a persistent pattern.

Getting Started Guide

If you need to use a bridge, follow these steps to minimize your risk. First, research the bridge thoroughly before using it. Check whether it has undergone professional security audits from reputable firms like Trail of Bits, OpenZeppelin, or ConsenSys Diligence. Look for audit reports published on the project’s website or documentation.

Second, check the bridge’s track record. Has it been operating for a long time without incidents? Projects that have been live for years without exploits generally have more battle-tested code. New bridges may offer better features but carry higher risk due to less testing in production environments.

Third, never bridge more than you can afford to lose. Even well-audited bridges can be compromised. Treat bridge transactions as high-risk operations and limit your exposure accordingly. If you need to move a large amount between chains, consider doing it in smaller transactions over time rather than all at once.

Fourth, prefer bridges that use verified multi-signature security models with transparent validator sets. Bridges that rely on a small number of validators or centralized control present higher counterparty risk. Look for projects that publish their validator lists and governance structures openly.

Common Pitfalls

New users often make several mistakes when using cross-chain bridges. The most dangerous is approving unlimited token spending. When you interact with a bridge, you typically need to grant it permission to spend your tokens. Some bridges request unlimited approval, which means if the bridge is later compromised, the attacker can drain all tokens you have approved, not just the amount you intended to bridge.

Another common mistake is rushing through transactions without verifying the destination address. Bridge interfaces can be spoofed by phishing sites, and sending tokens to the wrong address results in permanent loss. Always double-check the URL and verify the transaction details before confirming.

Users also frequently ignore bridge fees and slippage. Moving assets between chains costs money, and the exchange rate may not be exactly one-to-one. Factor in these costs when deciding whether bridging is worth it, especially for smaller amounts where fees might represent a significant percentage.

Next Steps

Once you understand bridge basics, consider exploring alternatives that may reduce your reliance on them. Some centralized exchanges offer free or low-cost internal transfers between networks, which can be safer for large amounts. Wrapped tokens on major DEXs sometimes offer liquidity paths that avoid bridge interaction entirely. As the ecosystem matures, new interoperability protocols like LayerZero and Chainlink’s CCIP aim to provide more secure cross-chain communication, potentially reducing the risks that current bridges present. Stay informed about these developments as they may offer safer options in the near future.

Disclaimer: This article is for informational purposes only and does not constitute financial or investment advice. Always conduct your own research before making any financial decisions.