Before you approve an unknown token, your wallet shows a warning that the gas fee is unusually high. Most likely, this is not network congestion. The contract you are about to interact with has a problem.
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What to Check
Determine whether the unusually high gas fee is caused by network conditions or contract risk, and do a risk check before confirming the approval.
Why Unusually High Gas Is a Risk
First, look at some data. In June 2025, more than 97% of approvals in EIP-7702 transactions went to the same malicious contract. This involved 48,000 addresses, and over 65% of the funds eventually flowed to the same hacker address. This shows that approval-related risk is not a rare event. It is already highly automated and happening at scale.
Unusually high gas usually means the contract is doing more than a normal approval. A normal ERC-20 approval only needs to call the approve function, and the gas cost is around 45,000 to 60,000. If the gas limit shown by your wallet is over 200,000 or even higher, the contract may contain extra logic:
Endless loop: Malicious contracts can contain code that keeps consuming gas until your gas limit is used up. The transaction eventually fails, but the gas fee is still deducted by the node.
Gas fee hijacking: A frontend controlled by an attacker can automatically set the gas price or gas limit to an extremely high level, far above normal network congestion levels.
Step-by-Step Risk Check
Case A: First check whether it is a network problem.
Open Etherscan and look at the current block base fee:
- If the base fee is in the normal range of 5-20 Gwei, the network is not congested. The high fee is caused by the contract.
- If the base fee is above 50 Gwei, network congestion may indeed be causing higher fees. But even during congestion, an approval transaction should not have a gas limit above 100,000.
Case B: Check the contract risk.
- Check the contract source. Enter the token contract address on Etherscan and look at the "Contract" tab. Is the contract open source? Has the code been audited? If the code is unreadable or the "Verified" status is gray, stop the operation immediately.
- Check the approval amount. Your wallet approval popup usually has an approval amount option. Refuse "Unlimited" or "Maximum" approval. Only approve the exact amount needed for this operation. This is a basic defense against having your assets transferred out in bulk.
- Use tools to check approval history. If you have already approved tokens before, use Revoke.cash or Etherscan's "Token Approval Checker" to regularly review and revoke unknown approvals.
- Simulate before confirming. Use a wallet like Rabby, which performs a full simulation before confirmation and directly shows the "Revert Reason." Or create a free Tenderly account and simulate the transaction result without spending any money.
High-risk warning: Do not sign an approval signature you do not understand. New standards like EIP-7702 allow a single approval to give a contract full control of your wallet. The interface may only show an unreadable hash. You may think it is a normal login verification, but after clicking confirm, your wallet can be emptied instantly.
Safe Approval Checklist
- The gas limit shown by your wallet is within a normal range. An ERC-20 approval should not exceed 60,000 to 80,000.
- The contract address is verified and open source on Etherscan.
- The approval amount is set to the exact amount needed for this operation, not "Unlimited."
- You have run the transaction through a simulation tool and no red warning appeared.
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FAQ
Q: The gas fee is unusually high, but I am afraid to click confirm. Is there a way to test it first? A: Use Tenderly's simulation feature. Enter the token contract address and the function you want to call. It will simulate the result and show the gas cost without costing you anything.
Q: I approved an unknown token, but I have not transferred anything yet. Do I need to pay gas to revoke the approval now? A: Yes. Revoking an approval, which means changing the approval amount to 0, is a separate on-chain transaction that requires gas. But paying this gas is far better than keeping a malicious approval. The latter could empty your wallet at any time.
