From a8562b5f355b1cfe1b4b1d1f18fb05fd30f7834d Mon Sep 17 00:00:00 2001
From: emmmm <155267286+eeemmmmmm@users.noreply.github.com>
Date: Wed, 2 Jul 2025 07:45:32 +0200
Subject: [PATCH] common/hexutil: improve hex string syntax validation in
 Decode function

---
 common/hexutil/hexutil.go | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/common/hexutil/hexutil.go b/common/hexutil/hexutil.go
index d3201850a8..01235cb0df 100644
--- a/common/hexutil/hexutil.go
+++ b/common/hexutil/hexutil.go
@@ -64,6 +64,14 @@ func Decode(input string) ([]byte, error) {
 	if !has0xPrefix(input) {
 		return nil, ErrMissingPrefix
 	}
+	
+	// Check for invalid characters before passing to hex.DecodeString
+	for i := 2; i < len(input); i++ {
+		if !isHexCharacter(input[i]) {
+			return nil, ErrSyntax
+		}
+	}
+	
 	b, err := hex.DecodeString(input[2:])
 	if err != nil {
 		err = mapError(err)
@@ -239,3 +247,8 @@ func mapError(err error) error {
 	}
 	return err
 }
+
+// isHexCharacter returns true if c is a valid hexadecimal character.
+func isHexCharacter(c byte) bool {
+	return (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F')
+}