From c16782e62a0f3544c0ac1e060bc01d0f9d24af97 Mon Sep 17 00:00:00 2001
From: samsamtrum <samsamtrum@users.noreply.github.com>
Date: Mon, 22 Jun 2026 02:17:49 +0700
Subject: [PATCH] Reject negative bigint hexlify values

---
 src/sdk/common/utils/hexlify.ts | 4 ++++
 test/hexlify.test.ts            | 8 ++++++++
 2 files changed, 12 insertions(+)
 create mode 100644 test/hexlify.test.ts

diff --git a/src/sdk/common/utils/hexlify.ts b/src/sdk/common/utils/hexlify.ts
index f0001b3..be2b9a7 100644
--- a/src/sdk/common/utils/hexlify.ts
+++ b/src/sdk/common/utils/hexlify.ts
@@ -91,6 +91,10 @@ export function hexlifyValue(value: BytesLike | Hexable | number | bigint, optio
     }
 
     if (typeof (value) === "bigint") {
+        if (value < 0n) {
+            throw new Error(`Invalid Hexlify value - negative bigint value: ${value}`);
+        }
+
         value = value.toString(16);
         if (value.length % 2) { return ("0x0" + value); }
         return "0x" + value;
diff --git a/test/hexlify.test.ts b/test/hexlify.test.ts
new file mode 100644
index 0000000..8bd2a03
--- /dev/null
+++ b/test/hexlify.test.ts
@@ -0,0 +1,8 @@
+import assert from 'node:assert/strict';
+import { hexlifyValue } from '../src/sdk/common/utils/hexlify.js';
+
+assert.equal(hexlifyValue(0n), '0x00');
+assert.equal(hexlifyValue(15n), '0x0f');
+assert.equal(hexlifyValue(16n), '0x10');
+assert.throws(() => hexlifyValue(-1n), /negative bigint value/);
+assert.throws(() => hexlifyValue(-16n), /negative bigint value/);