Attackers exploited a critical vulnerability in Wanchain's Cardano-to-BNB Chain bridge on July 21, 2026, draining approximately 515 million NIGHT tokens, valued near $13 million. This exploit demonstrates how a subtle cryptographic flaw can translate into massive token inflation in DeFi infrastructures.

The root cause was a signature reuse vulnerability in the TreasuryCheck validator. Wanchain’s message signing concatenated 14 variable-length fields without delimiters or length prefixes. This allowed attackers to create different field combinations producing identical hash values, effectively bypassing authorization limits. An original signature meant for about 3,110 NIGHT was manipulated to mint over 203 million NIGHT in one transaction, causing a 65,000-fold inflation effect.

This method of attack highlights how complex bridging systems remain fragile when cryptographic integrity is compromised. The immediate market reaction was swift: NIGHT’s price plummeted over 30% to a historic low near $0.016 after the sudden influx of stolen tokens flooded decentralized exchanges. Such dumps erode investor confidence and illustrate the liquidity risks inherent in bridge exploits.

Importantly, the Midnight Foundation clarified that their core network and validators were unaffected by the breach. The compromise was strictly isolated to the third-party bridge infrastructure’s treasury, which manages token custody during cross-chain transfers rather than the overall token supply capped at 24 billion NIGHT. This separation shows the ongoing challenge of interconnectivity in cross-chain ecosystems where third-party components can become weak links.

Wanchain responded by taking the bridge offline and committing to a full technical post-mortem. Security firm BlockSec noted that the bridge neglected to use Cardano's SerialiseData function when hashing signatures a safeguard that might have prevented the exploit. This case underlines the imperative for bridges to implement solid cryptographic standards to avoid replay or signature forgery attacks.

This incident adds to a growing list of costly bridge hacks that stress the vulnerability of decentralized liquidity channels and emphasize the need for more rigorous smart contract auditing and architectural redesigns.