Bridge hacks explained: The vulnerability of cross-chain bridges.

Bride hacks affect the entire crypto ecosystem, as bridges connect and maintain the vast crypto network.Cryptocurrency development aims to be decentralized, not isolated. Initially, plans were made for projects like Ethereum, Solana, BNB, and others to operate independently. However, a problem arose that made them realize they were not capable of connecting with each other.

This is where cross-chain bridges come into play. The biggest hacks in the history of crypto have occurred as a result of bridge hacks, which cost the industry a huge sum of money. Here is a thorough explanation of how the bridges are susceptible to hacking.

NOTE: Crypto investments involve significant risk. Do not take the views mentioned here as financial advice. Please conduct thorough research before making any investment.

What is a Cross-Chain Bridge?

Representative image for the large crypto network (Image via Unsplash/@kanchanara)

The cross-chain bridge service permits the transfer of crypto-assets between blockchains. The cross-chain bridge service permits transferring crypto assets from one blockchain.

For example:

You lock ETH on Ethereum.
The bridge distributes wrapped ETH on a different chain, such as Solana or Polygon.
The wrapped tokens are destroyed when returning, so the original ETH is released.

That sounds simple, but internally, it is very complicated.

Why do hackers favor bridge hacks?

1) The bridges carry large sums of money. The role of bridges is similar to that of a central vault, which locks away millions, perhaps even billions, of dollars in bridge smart contracts. The return on a single bridge hack is massive.

For hackers, bridges are a valuable resource with a single point of failure.

2) Complex code means more bugs

Bridge systems consist of:
Multiple blockchains
Smart contracts on each chain
Validators/Relayers
Oracles, message passing logic

The more layers, the greater the attack surface.

More complexity means:

More opportunities for coding errors
Logic flaws that audits may miss
Application edge cases that can be used by attackers

3) Weak or centralized validation

Most bridges are supported by a small group of validators, multisig wallets with limited signers, and off-chain verification systems.

If attackers find out private keys, utilize weak key management, and use social engineering to trick validators, they can mint unlimited fake tokens as well as unlock locked funds. That is why some decentralized bridges fail in very centralized ways.

4) The bugs in smart contracts are highly expensive.

Vulnerabilities commonly identified in a bridge hack include:

Reentrancy attacks – attacking while balances are updated.
Inappropriate message verification, which accepts illegitimate cross-chain messages.
Incorrect signature validation.
Replay attacks over the chains.

After the implementation, the smart contracts are mostly immutable; hence, bugs cannot be easily corrected.

5) Cross-chain messaging is hard to secure from bridge hacks

The job of a bridge is not merely to move tokens but messages from two different chains. If a hacker sets a message, bypasses verification logic, or uses timing delays, they can deceive the destination chain into believing that the funds were locked when, in fact, that never happened. It ensures that the attacker can forge tokens from scratch.

The real-life effects: The problem with bridge hacks

When a bridge hack happens:

Trust is broken instantly.
The pegged assets can remain unhedged.
Ecosystems are subjected to a liquidity shock.
Users may own tokens whose value suddenly drops to zero, even when they have broken no law..

It is not only the crypto protocols that get harmed by a bridge hack, but also the regular investors.

Why audits alone are not enough:

Many hacked bridges were:

already audited
believed to be supported by big investors
commonly used in top DeFi projects

Why audits fail:

Audits are time-bound, done intermittently.
They may not cover all edge cases.
Attackers have unlimited time to find vulnerabilities.

Security is not a box that is checked once, but an uninterrupted process

Are all bridges unsafe? The fact is, not all bridges are alike when it comes to safety standards.

The return on a single bridge hack is massive. For hackers, bridges are a valuable resource with a single point of failure.

Relatively safer designs include:

Bridges native to L1 blockchains.
Limited client-based bridges with on-chain verification.
Bridges that use decentralized validation sets.
Protocols with bug bounties and real-time analysis.

Nonetheless, even the best bridge is inherently unsafe.

What users can do to stay safe from bridge hacks

Here are ways for common users to reduce risks:

Avoid keeping large funds on bridges.
Bridge only what you need, when you need it.
Choose native or well-established bridges; they generally have a greater incentive to remain secured.
Watch for wrapped token risks; the wrapped assets are entirely dependent on the health of the bridge.
Monitor security news. Often, bridge issues are identified on-chain before the official announcement.

The future of cross-chain security

The sector is actively engaged in:

Trust minimized bridges
Zero-knowledge proof cross-chain verification
Better on-chain visibility
Shared security models

However, for now, bridges are still the most targeted infrastructure within the crypto sector.

Cross-chain bridges are vital for a multi-chain future, but they are an Achilles heel for cryptos. They mean high-value assets, extreme complexity, and partial centralization, making them irresistible to hackers for bridge hacks.

Knowledge of bridge hacks helps make smarter and safer decisions when improved modifications for a globally interwoven crypto network are taken.

Edited by Adarsh J Kumar