Definition
A bridge hack is a type of security incident in which a malicious actor compromises a blockchain bridge and gains unauthorized control over the assets or data it handles. Because a bridge connects two or more blockchains, a successful attack can affect value represented as bridged assets on one or multiple networks. The hack typically targets weaknesses in the bridge’s design, implementation, or operational controls, turning the bridge into a high-impact attack surface.
In a bridge hack, the attacker usually aims to forge, redirect, or unlock transfers that should not be authorized, allowing them to drain or misrepresent bridged assets. The risk arises from the bridge’s central role in validating and coordinating cross-chain messages, which, if subverted, can break the expected correspondence between assets locked on one chain and their representations on another. As a result, a bridge hack can undermine trust in the affected bridge and in any bridged asset that depends on it.
Context and Usage
The term bridge hack is used to describe incidents where attackers exploit the specific mechanisms that allow a bridge to verify and relay information between chains. These mechanisms can include smart contracts, external validators, or off-chain components that collectively form the bridge’s attack surface. When any of these components are compromised, the attacker may be able to create fraudulent messages or bypass normal checks to seize control of funds.
Bridge hacks are often discussed alongside bridge exploit, a closely related phrase that emphasizes the technical method used to trigger the failure. In practice, a bridge hack highlights the systemic risk that arises when large amounts of value are concentrated in a single cross-chain connection. The concept underscores that the security of bridged assets depends not only on the underlying blockchains, but also on the robustness of the bridge that links them.