In a notable security breach, the 402bridge protocol experienced a hack on October 28, 2025, resulting in over 200 users losing their USDC. The hack was due to a private key leak in the backend system of the protocol, which shook the DeFi space in the user security aspect.
Understanding The 402bridge Hack
The vulnerability was discovered by GoPlus Security and revealed that unauthorized token transfers were being performed because of high user authorizations. The attackers used these loopholes to steal around $17,693 worth of USDC from linked wallets. This attack followed a record spike in the usage of the platform as there was a 500% hike in token value, putting the sufficiency of its security controls in question.
What Caused the Breach
The hack was published shortly after the 402bridge had launched on-chain. A report states that the owner of the contract transferred ownership to another address and granted the new owner admin rights. The transfer gave the hacker access to sensitive operations, such as the “transferUserToken” function, which withdrew funds from vetted users.
Excessive authorization enabled the attackers to steal funds from over 200 impacted users, with most losing stablecoins due to these abuses of the minting process.
Swift Responses to the Incident
Following the hack, 402bridge has moved swiftly in an attempt to prevent losses. The protocol has suspended all activities and brought its website down and reported the matter to the police. Users should revoke any current authorizations related to the 402bridge to prevent further unauthorized transactions.
402bridge confirmed that the hack was due to a leak of private keys, impacting a number of wallets used for testing and for regular operations. Users should exercise utmost care when allocating unlimited token allowances and ensure their wallet authorizations are current by conducting frequent audits to enhance security.
