What are Cross-Chain Bridge Attacks? How To Tackle Them?

by ImmuneBytes


Cyberattacks are more likely when blockchain technology and cryptocurrencies are used more frequently. The cross-chain bridge attack, which takes advantage of flaws in the systems that permit the transfer of digital assets between several blockchain networks, is one specific form of assault that has drawn attention recently. The security and integrity of blockchain ecosystems are seriously threatened by these attacks, which can take many different forms. In this post, we will examine cross-chain bridge attacks, various attack types, and defence strategies. Blockchain developers and operators may improve the security of their systems and better safeguard their digital assets by recognising these attacks and following best practises to reduce the risk.

What are cross-chain bridge protocols?

Cross-chain bridges are mechanisms that allow for the transfer of digital assets between different blockchain networks. They are an essential component of decentralized finance (DeFi) applications, which aim to enable trustless, peer-to-peer financial transactions. However, the very features that make cross-chain bridges so useful, namely their decentralization and openness, also make them vulnerable to attack.

Despite the fact that bridge designs can vary, most cross-chain bridge interactions include users transmitting money in one asset to the bridge protocol, where it is subsequently locked into the contract. A counterpart asset on the chain that the protocol bridges to is subsequently issued to the user in the equivalent amount. In the case of Wormhole, customers often submit ETH to the protocol, where it is held as collateral, and are then granted ETH that has been wrapped around the Wormhole token on Solana. This ETH is secured by the ETH that was sent as collateral and locked in the Wormhole contract on Ethereum.

How do cross-chain bridges work?

Most cross-chain bridges use the “Lock & Mint” and “Burn & Release” modes, and here is how they operate.

For instance, let’s consider Chain 1 as one blockchain network and Chain 2 as another blockchain network.

The Lock & Mint technique allows for the creation of a bridge to lock a predetermined quantity of tokens on Chain 1 and mint new ones on Chain 2. As an illustration, if Chain 1 had 100 tokens and transferred 50 of them to Chain 2, Chain 1 would still display 100 tokens, but 50 of those would be locked, and 50 tokens would (be mint) now appear on Chain 2.

The owner of newly created 50 tokens on Chain 2 has the option to “release” or unlock them entirely from Chain 1 or to redeem them or “burn” them from Chain 2. The Burn & Release technique is used for this.

Both models and methods guarantee that the number and price of tokens moved between Chains 1 and 2 are always consistent.

What makes cross-chain bridges so vulnerable?

Cross-chain bridges are decentralized systems that facilitate the transfer of digital assets between different blockchain networks. While they offer many benefits, including interoperability, faster transaction times, and reduced transaction fees, they are also inherently vulnerable to attack due to their openness and decentralization.

  1. One of the primary reasons why cross-chain bridges are vulnerable to attack is that they rely on multiple parties to operate. These parties, which can include validators, oracles, and users, must all work together to ensure the security and integrity of the bridge. 
  1. The fact that cross-chain bridges frequently rely on smart contracts to carry out transactions automatically is another weakness. While smart contracts can increase transparency and limit the possibility of human error, they are nevertheless susceptible to programming flaws and other types of code exploits that can be used by attackers. The transaction data may be altered or manipulated by a hacker who has access to the smart contract, opening the door to the theft of digital assets or other nefarious deeds.
  1. Finally, cross-chain bridges are frequently intricate systems that need several defences against intrusion. The potential for vulnerabilities and weaknesses grows as system complexity rises, making it more challenging to spot security flaws and fix them before attackers take advantage of them.

What are Cross-Chain Bridge Attacks?

Cross-chain bridge attacks are a type of cyberattack that exploit vulnerabilities in the mechanisms that enable the transfer of digital assets between different blockchain networks. These attacks can take many different forms and can compromise the security and integrity of the entire blockchain ecosystem.

  1. One common type of cross-chain bridge attack is the “man-in-the-middle” attack, where an attacker intercepts communications between the two blockchain networks connected by the bridge and manipulates the transaction data to steal digital assets or redirect them to a different address. This type of attack is particularly effective against bridges that rely on centralized intermediaries, such as validators or oracles, which can be compromised to gain access to the system.
  1. Another type of cross-chain bridge attack is the “double-spending” attack. In this scenario, the attacker sends a transaction on one blockchain network, receives the digital assets, and then quickly sends another transaction on the other blockchain network to receive the same assets again. By exploiting a vulnerability in the cross-chain bridge, the attacker can effectively double-spend the digital assets, leading to a loss for the victim of the attack.
  1. Other types of cross-chain bridge attacks include denial-of-service attacks, where an attacker floods the system with transaction requests to overload and disrupt the functioning of the bridge, and parameter manipulation attacks, where an attacker modifies the parameters of the bridge to execute fraudulent transactions or gain unauthorized access to the system.

How to tackle Cross-Chain Bridge Attacks?

For blockchain developers and security professionals, combating cross-chain bridge attacks is a difficult and constant task. The likelihood of these attacks can be reduced by a number of best practises, though.

First and foremost, the entire blockchain ecosystem needs to be covered by robust security mechanisms. This entails employing reliable encryption and authentication systems, updating software and firmware often, and carrying out regular security audits and vulnerability analyses.

Second, to guarantee that only authorised users have access to sensitive data and transactional operations, blockchain developers and operators should incorporate stringent access controls and permission levels.

Finally, the use of smart contracts and other automated mechanisms can help to improve the security of cross-chain bridges by reducing the potential for human error or malicious actions. Smart contracts can automate the execution of complex transactional processes and provide a transparent and auditable record of all transactions.

What are the best cross-chain bridges currently? 

These are the top cross-chain bridges in 2023 among several other widely used ones.

Polkadot (DOT): Developers can create unique chains called Parachains on Polkadot, dApps, and blockchain. On the Polkadot network, the relay chain here offers security and permits the secure movement of assets between Parachains.

Polygon (MATIC): To facilitate the transfer of digital tokens and NFTs, a cross-chain bridge connects the Polygon sidechain with the Ethereum mainnet. Low gas prices and increased security are also features of this cross-chain bridge.

Avalanche (AVAX): Tokens can be transferred between AVAX and Ethereum via this cross-chain bridge. AVAX is among the quickest smart contract platforms and one of the earliest creators of cross-chain bridges.

Binance(BNB): BNB Smart Chain (BSC) supports the most popular programming languages, flexible tools, and comes with clear and canonical documentation.


Blockchain ecosystem security and integrity are being threatened by cross-chain bridge attacks. But, the risk of these attacks can be reduced by putting in place robust security protocols, access limits, and smart contract mechanisms. There will probably be more and more advanced cross-chain bridge attacks as the blockchain business develops and grows. It is crucial that security professionals and blockchain developers continue to be proactive in their attempts to counter these threats.

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