Incident Overview
On June 19, 2025, the Bankroll Network DeFi protocol suffered an exploit resulting in a loss of approximately $65,000 due to an integer underflow vulnerability in its sell() function on both Ethereum and Binance Smart Chain.
The attacker exploited a legacy integer underflow vulnerability in the sell() function of the BankrollNetworkStack contract, which was compiled with Solidity 0.6.8—a version that does not automatically revert on arithmetic underflows. By manipulating dividend payout calculations using signed integers without proper checks, the attacker caused erroneous balance adjustments that allowed them to drain funds. This exploit affected users who had previously interacted with or approved the compromised contracts.
Notably, this is the second known exploit of Bankroll Network, following a $235K hack in September 2024.
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 Bankroll, these are the critical security checks that could have prevented this incident (June 2025).
- 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
Master these auditing techniques with hands-on labs and real exploit scenarios in the Smart Contract Hacking course.
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