From 5052910fba8c7b53169cf4e5b1c57fc9f105734f Mon Sep 17 00:00:00 2001
From: MariusVanDerWijden <m.vanderwijden@live.de>
Date: Wed, 10 Sep 2025 10:24:28 +0200
Subject: [PATCH] core/vm: fix modexp gas calculation

---
 core/vm/contracts.go | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/core/vm/contracts.go b/core/vm/contracts.go
index 5d72fe4ac1..77fac2f907 100644
--- a/core/vm/contracts.go
+++ b/core/vm/contracts.go
@@ -469,9 +469,12 @@ func modexpIterationCount(expLen uint64, expHead uint256.Int, multiplier uint64)
 
 	// For large exponents (expLen > 32), add (expLen - 32) * multiplier
 	if expLen > 32 {
-		iterationCount = (expLen - 32) * multiplier
+		carry, count := bits.Mul64(expLen-32, multiplier)
+		if carry > 0 {
+			return math.MaxUint64
+		}
+		iterationCount = count
 	}
-
 	// Add the MSB position - 1 if expHead is non-zero
 	if bitLen := expHead.BitLen(); bitLen > 0 {
 		count, carry := bits.Add64(iterationCount, uint64(bitLen-1), 0)