Introduction to Common Security Vulnerabilities in Cross-Chain Bridges
Cross-chain bridges connect different blockchains and facilitate cross-chain assets, making them frequent attack targets. Understanding validation flaws, differences in token handling, and configuration risks is fundamental to learning about cross-chain security.
Why Cross-Chain Bridges Require Strong Protection
Cross-chain bridges enable assets and messages to move between different blockchains, typically using smart contracts to custody or process large amounts of tokens. Because the process involves on-chain contracts, off-chain servers, signers, and configuration permissions, a flaw at any point can expand the attack surface and cause assets to be released or minted incorrectly.
On-Chain and Off-Chain Validation Risks
If on-chain validation does not correctly check signatures, transaction proofs, recipient addresses, or replay conditions, attackers may forge deposits and mint tokens. Off-chain servers should also verify that deposit transactions actually occurred, that the event structure is correct, and that the events were emitted by trusted contracts; otherwise, malicious contracts could imitate events and trick signers into producing valid signatures.
Token Handling and Authorization Risks
Native tokens and ERC-20 tokens are deposited differently: the former can read the amount from msg.value, while the latter typically relies on approval and transferFrom or burnFrom. If functions are mixed up, return values from external calls are not checked, or whitelist or zero-address logic is incorrect, assets may be lost or uncollateralized withdrawals may occur.
Configuration Management and Security Hardening
Privileged roles in cross-chain bridges can adjust critical settings such as token lists, address lists, and signers. Incorrect default values or upgrade configurations may cause invalid messages to be automatically treated as valid. Projects should test various attack paths around their own validation logic, conduct comprehensive testing before deployment, and engage a third-party security audit.
Original Tutorial
https://www.binance.com/zh-CN/academy/articles/what-are-common-bridge-security-vulnerabilities
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