Incident Overview
In 18th June 2026, the privacy-focused Layer 2 protocol Aztec Network suffered a smart contract exploit on Ethereum mainnet targeting its legacy PrivateRollupBridge contract, resulting in a loss of approximately $2.19 million.
This incident is structurally related to the previous exploit on June 14, targeting an immutable Stage 2 rollup deployment that was officially sunset in 2022. Because the contract is entirely immutable, the team lacked admin keys to freeze or update the vulnerable architecture.
The attacker capitalized on the contract’s open escapeHatch() window, a mechanism allowing emergency withdrawals under specific block intervals. Within the payload, the attacker submitted malformed proofData where the parameters for rollupSize and numTxs were explicitly set to zero. However, the contract's internal proof verification function, verifyProofAndUpdateState(), contained a logic floor that automatically defaulted the execution transaction count (numTxs) to a minimum value of 1. This mathematical discrepancy allowed the verification layer to evaluate a zero-transaction block, while the downstream execution logic (processDepositsAndWithdrawals()) parsed and validated the malicious withdrawal commands attached right after the proof header, enabling the unauthorized extraction of assets.
Vulnerable Contract Address: 0x737901be…42a2ba (Private Rollup Bridge)
Attacker Address: 0x6952d924…78E97F
Primary Attack Transaction: 0xab306cd2…59c2b5
Incident Report
Protocol Information
What the Attacker Needed to Succeed
Understanding the prerequisites for this type of attack helps auditors identify protocols that are most at risk and helps developers build better defenses.
What Auditors Should Check
If you're auditing a protocol with similar architecture to Aztec, these are the critical security checks that could have prevented this incident (June 2026).
- Verify all logic paths related to Other are guarded by proper access controls and input validation
- Review privileged functions (owner, admin, governance) for potential abuse vectors - centralization risks should be documented and bounded with timelocks or multi-sigs
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