Hyperhyper — option premium is priced on the short input period

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 57738-h-01-option-premium-calculation-underprices-options-pashov-a. Standalone Foundry PoC and full write-up: 57738-h-01-option-premium-calculation-underprices-options-pashov-a_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/logic/price-calculation · vuln/logic/fee-calculation · vuln/logic/incorrect-calculation

Reproduction: a self-contained Foundry PoC that compiles and runs offline with only forge-std — no fork and no RPC. Trace: output.txt. PoC: test/57738-h-01-option-premium-calculation-underprices-options-pashov-a_exp.sol.

Key info#


Impact	HIGH — the buyer pays 7 ether and the seller is short 999976851851851851 wei
Protocol	Hyperhyper `Strategy._calculatePremium`
Vulnerable code	`optionPrices(period, ...)` instead of the rounded maturity
Bug class	Premium uses a shorter time than the option actually lives
Finding	Pashov Audit Group — Hyperhyper, 30 March 2025 · H-01 · id 57738
Report	Hyperhyper-security-review_2025-03-30.md
Source	AuditVault finding
Status	Reproduced with the audited maturity rounding and a linear time value
Compiler	solc 0.8.27, cancun, via IR

TL;DR#

_computeMaturityDate rounds expiry up to the last second of the day, so a 7-day input lasts longer than 604800 seconds. _calculatePremium still calls optionPrices with the input period.

On the replay timestamp the charged premium is 7 ether (365 ether * 7 days / 365 days). The fair premium, using the rounded maturity, is 7999976851851851851 wei. The seller who hedges at the fair value is short 999976851851851851 wei.

Pricing optionPrices with maturity - block.timestamp makes charged equal fair. The short is 0.

The vulnerable code#

SOLIDITY

function _computeMaturityDate(uint256 period) public view returns (uint256 maturityTimestamp) {
    maturityTimestamp = block.timestamp + period;
    maturityTimestamp -= (maturityTimestamp % 1 days);
    maturityTimestamp += 1 days - 1;
}

premium = bs.optionPrices(period, notional);

The time value in this reduction is notional * time / 365 days, so the only difference between the two quotes is the time argument. The report's Black-Scholes numbers show the same direction: a 7-day call quoted at 8963759233891000000 against a maturity quote of 11675104193168500000.

Root cause#

The option's lifetime and the time passed into the pricer are different values. Maturity is stored rounded up. The premium is not.

Preconditions#

period is 7 days.
block.timestamp + period is not already the last second of a day, so the round-up adds time. It does on this block.

Attack walkthrough#

Read actualDuration(7 days). It is greater than 604800.
buy charges optionPrices(period) which is 7 ether, and pulls that from the buyer.
The seller pays the buyer the fair hedge, optionPrices(actualDuration).
The buyer's balance rises by the gap. The seller's reserve falls by the same gap.

Control: StrategyFixed.buy passes actualDuration(period) into optionPrices. Charged equals fair. Both balances are unchanged apart from the round trip. The short is 0.

Diagrams#

flowchart TD A["Input period is 7 days"] --> B["Maturity is rounded up to the end of the day"] B --> C["optionPrices is called with the input period"] C --> D["Buyer pays 7 ether"] D --> E["Seller hedges the longer maturity and is short the gap"]

Impact#

The buyer pays less than the time they receive. Here that discount is 999976851851851851 wei on a 7 ether quote, and the seller is short exactly that amount. The fixed quote charges the fair premium and the short is 0.

Remediation#

Pass maturity - block.timestamp into optionPrices, not the raw period argument.

Sources#

Taxonomy#

severity/high
vuln/logic/price-calculation · vuln/logic/fee-calculation · vuln/logic/incorrect-calculation

Sources & further analysis#

Reproductions & code

Standalone PoC + full trace: 57738-h-01-option-premium-calculation-underprices-options-pashov-a_exp (evm-hack-registry mirror).
AuditVault finding: 57738-h-01-option-premium-calculation-underprices-options-pashov-a.

Alerts & third-party analyses

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