Wanchain took its Cardano-to-BNB Chain bridge offline on July 21, 2026, after attackers drained approximately 515.2 million NIGHT tokens from the bridge treasury in a signature-reuse exploit.
Key Takeaways
- Wanchain’s Cardano bridge lost approximately 515.2 million NIGHT tokens, worth approximately $10 million, across four transfers in eight minutes.
- A single valid signature authorized a payout about 65,000 times larger than Wanchain approved, per BlockSec’s review.
- Wanchain’s bridge never used Cardano’s SerialiseData function, which BlockSec found already sitting in the contract, to build the signature check.
- The attacker sold roughly 300 million NIGHT on exchanges, pushing the token down more than 30% to a record low near $0.016.
- The Midnight Foundation said its protocol, validators, consensus system and core infrastructure kept operating normally throughout the incident.
What Happened?
The bridge has been offline since the exploit, per Wanchain, which said The Wanchain Bridge is currently unavailable to users. We are committed to full transparency and will share an update as soon as our investigation is complete.
Wanchain has not published a compensation or restoration timeline. Some of the stolen tokens already moved onto exchanges, per BlockSec’s on-chain trace.
The drain moved fast, according to BlockSec, an on-chain forensics firm whose Phalcon system flagged the exploit. The theft ran through four rapid transfers to one attacker wallet, totaling roughly 203.0 million, 129.6 million, 120.4 million, and 62.1 million NIGHT, an automated sequence, not a slow leak.
BlockSec: Wanchain Cardano Bridge Reportedly Exploited, 515M NIGHT Drained
— Wu Blockchain (@WuBlockchain) July 21, 2026
BlockSec’s Phalcon said Wanchain’s Cardano bridge was reportedly exploited, with approximately 515 million NIGHT drained from the bridge treasury. Initial analysis suggests the issue may stem from… pic.twitter.com/7u1LHOlWul
How the Signature Reuse Worked?
BlockSec traced the root cause to a non injective signed message flaw in the bridge’s TreasuryCheck validator. Wanchain built its signed message by raw-concatenating 14 variable length redeemer fields without delimiters or length prefixes, which let different field combinations collapse to the same byte string and hash.
That design is a textbook signature reuse setup. Without clear field boundaries, a hash function cannot tell two different inputs apart, so one valid signature covers both.
The gap let the attacker reuse a legitimate signature that had authorized only about 3,110 NIGHT to extract 203,001,692 NIGHT in a single transaction. BlockSec also noted that the contract already contained Cardano’s SerialiseData function but did not call it when building the signature hash.
Using it with a hash function would have produced clear CBOR-encoded field boundaries and blocked the collision. The safeguard did not need inventing. It shipped with the code and sat unused, turning an unavoidable zero-day into a wiring mistake a pre-launch audit should have caught.
Cardano and Midnight Network Say Core Protocol Is Unaffected
The Midnight Foundation moved to separate the bridge failure from the Cardano-linked network it governs, saying the incident is isolated to the Wanchain Cardano-BNB bridge and does not involve the Midnight Network itself.
The foundation added that the affected tokens were bridged NIGHT held in the Wanchain bridge treasury rather than tokens taken from the Midnight network’s own ledger. The foundation said it currently sees no evidence the incident touched the network’s security or operational integrity.
That distinction matters for how the loss should be read. Bridges are connective tissue bolted onto a Layer 1, not the Layer 1 itself. Bridge code keeps failing while the chains it connects keep running underneath it.
CoinLaw’s Takeaway
This exploit is a preventable bug story before it is a bridge security story. BlockSec’s own writeup shows Cardano’s SerialiseData function sitting inside the Wanchain contract the whole time, unused for the one job that would have stopped the collision: giving the signature hash clean boundaries between fields.
A validator that concatenates 14 variable length inputs without delimiters is not an exotic attack surface. It is a known class of bug with a known fix already sitting in the codebase, which puts the failure on integration and review, not on some undiscoverable flaw in Cardano’s design.
The Wanchain-Midnight split also previews how this kind of loss tends to get reported going forward. The token that lost value was Midnight’s NIGHT, but the code that failed belonged to Wanchain, an outside interoperability layer with no operational tie to Midnight’s validators or consensus.
Reading the two as one event blurs a distinction that actually protects users. A bridge exploit drains what sits in the bridge, not what sits on the chain it connects to. Treasuries that route through outside bridge infrastructure carry that exposure regardless of how secure the underlying chain is, and that gap is where the next version of this story is most likely to come from.
