Index: /trunk/src/VBox/Devices/Network/DevVirtioNet.cpp
===================================================================
--- /trunk/src/VBox/Devices/Network/DevVirtioNet.cpp	(revision 67969)
+++ /trunk/src/VBox/Devices/Network/DevVirtioNet.cpp	(revision 67970)
@@ -1151,4 +1151,6 @@
 DECLINLINE(void) vnetCompleteChecksum(uint8_t *pBuf, size_t cbSize, uint16_t uStart, uint16_t uOffset)
 {
+    AssertReturnVoid(uStart < cbSize);
+    AssertReturnVoid(uStart + uOffset + sizeof(uint16_t) <= cbSize);
     *(uint16_t*)(pBuf + uStart + uOffset) = vnetCSum16(pBuf + uStart, cbSize - uStart);
 }