Merge pull request #4282 from assimp/kimkulling-fix_heap_overflow_during_utf8_issue4230

Make sure no overflow can happen

code/Common/BaseImporter.cpp

@@ -65,6 +65,7 @@ using namespace Assimp;
 // Constructor to be privately used by Importer
 BaseImporter::BaseImporter() AI_NO_EXCEPT
         : m_progress() {
+    // empty
 }
 
 // ------------------------------------------------------------------------------------------------
@@ -372,7 +373,10 @@ void BaseImporter::ConvertToUTF8(std::vector<char> &data) {
 
     // UTF 16 BE with BOM
     if (*((uint16_t *)&data.front()) == 0xFFFE) {
-
+        // Check to ensure no overflow can happen
+        if(data.size() % 2 != 0) {
+            return;
+        }
         // swap the endianness ..
         for (uint16_t *p = (uint16_t *)&data.front(), *end = (uint16_t *)&data.back(); p <= end; ++p) {
             ByteSwap::Swap2(p);