PrimeFinance: Stale Signed Oracle Report Drains Hyperliquid EVM Lending Pool

A missing timestamp check in PrimeFinance's DataStreamConsumer allowed an attacker to replay a legitimately signed but 11-month-expired Chainlink DON report, repricing PRFI 52× and draining ~425 WHYPE from the lending reserve.

Root Cause

DataStreamConsumer.verifyReport() validated the Chainlink DON signature but never enforced the report's expiresAt field. A real signed report bearing expiresAt = 2025-11-01 was accepted on 2026-09-16 — nearly 11 months after expiry. Signature validity and data freshness are orthogonal; the contract treated them as equivalent.

// Vulnerable pseudocode
function verifyReport(bytes calldata signedReport) external {
    // ✅ Checks DON signature — proves provenance
    address signer = recoverSigner(signedReport);
    require(isValidDONSigner(signer), "bad signer");

    // ❌ Missing freshness gate:
    // require(report.expiresAt >= block.timestamp, "stale report");

    // Price applied without age check
    _applyPrice(report.feedId, report.price);
}

Because verifyReport() is external with no role gate, any address can call it with historical reports pulled from on-chain calldata.

Attack Steps

Step	Action	Detail
1	Fund	Funded via Tornado Cash equivalent
2	Flash-loan	Borrowed 100 WHYPE from Morpho Blue on Hyperliquid EVM
3	Stale report replay	Called `verifyReport()` twice with valid DON-signed reports captured from historical calldata
4	Price manipulation	PRFI oracle price updated $0.0021 → $0.1101 (~52× increase)
5	Collateral deposit	Deposited PRFI at inflated valuation
6	Drain	Borrowed WHYPE against overvalued collateral, repaid flash loan
7	Profit	Net ~397–398 WHYPE extracted; 425.52 WHYPE total drained from reserve

Exploit tx: 0xff990876d863a61732779c341991215856c89420b84daaf31eece7ecd5ff4243
Attacker: 0x19bc1c7fd4aa93f540498499b8f5b4fc3dde5a52

Impact

~425.52 WHYPE drained from PrimeFinance's lending reserve on Hyperliquid EVM
PRFI token holders experienced artificial price distortion during the window
Protocol paused further borrows after detection
USD value unconfirmed (WHYPE price at block time not yet independently verified)

Lessons for Auditors

Separate authenticity from freshness. A valid DON signature proves a report came from Chainlink's network — it says nothing about whether the data is current. The expiresAt field in Chainlink Data Streams exists for exactly this purpose; check it with require(report.expiresAt >= block.timestamp, "stale").
Access-control verifyReport(). If price updates must flow from a keeper or protocol-controlled bot, restrict callers rather than leaving the function fully permissionless. Any open price-push surface is an attack vector.
Audit historical calldata surfaces. On-chain calldata is public and permanent. If old transactions contain validly-signed payloads, assume adversaries will replay them.
Pair oracle freshness with collateral factor limits. Protocols with thin long-tail asset markets should use tighter staleness bounds and lower LTV ratios to reduce the delta an attacker can arbitrage before detection.