Incident Overview
On April 23, 2026, Giddy DeFi lost $1.3M when an attacker exploited incomplete EIP-712 signature coverage in GiddyVaultV3. The signature only validated the data bytes of SwapInfo structs but not the aggregator, fromToken, toToken, or amount fields. This allowed the attacker to replay a valid signature while substituting the strategy's LP tokens with a malicious aggregator contract.
GiddyVaultV3 had a critical flaw in how it validated transactions using EIP-712 signatures. The signature only covered the data bytes portion of swap information but completely ignored other critical parameters like which aggregator contract to use, which tokens were involved, and how much to transfer.
The attacker grabbed a valid signature from a real transaction and replayed it with completely different parameters. They swapped in the vault's valuable LP tokens as the fromToken and pointed the aggregator to their own malicious contract. For the toToken they used a worthless fake token they created, and set the amount to MAX_UINT256 to drain as much as possible. The vault accepted this because the signature technically validated. It checked the data hash which hadn't changed, but never verified the swapped parameters. The result was LP tokens flowing out to the attacker's contract while worthless tokens came back.
Exploit Transaction: 0x5edb66a4…5482e5
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 Giddy, these are the critical security checks that could have prevented this incident (April 2026).
- Verify all logic paths related to Access Control are guarded by proper access controls and input validation - see the Access Control Attacks attack class for patterns
- 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.
Free TrialRelated Attack Classes
The technique used in this hack maps to these vulnerability classes in our security curriculum:
Sources & References
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