Missing Deadline Remediation

Overview

A transaction can sit in the mempool for a long time before a validator includes it. For price-sensitive operations — swaps, liquidity provision, mints priced off a curve — a stale execution can settle at a price the user would never have accepted. A deadline lets the user cap how long their signed intent remains valid. Omitting it, or hard-coding block.timestamp or type(uint256).max, removes that protection.

Recommended Fix

Before (Vulnerable)

function swap(uint256 amountIn, uint256 minOut) external {
    // No deadline: this can be mined hours later at a much worse price,
    // still passing the (now stale) minOut chosen when the tx was signed.
    _swap(amountIn, minOut);
}

After (Fixed — enforce a real, caller-supplied deadline)

error DeadlinePassed();

function swap(uint256 amountIn, uint256 minOut, uint256 deadline) external {
    if (block.timestamp > deadline) revert DeadlinePassed();
    _swap(amountIn, minOut);
}

The caller (or the front end) sets deadline to a short window — often a few minutes. Combined with a meaningful minOut slippage bound, this ensures the trade either executes near the intended price or reverts.

Common Mistakes

Accepting a deadline parameter but passing block.timestamp from within the contract, which makes the check always pass.
Setting the front-end default to type(uint256).max, which disables the protection while appearing to support it.
Relying on the deadline alone without a minAmountOut; the deadline bounds time, not price.