Index: /trunk/src/VBox/NetworkServices/NAT/pxping_win.c
===================================================================
--- /trunk/src/VBox/NetworkServices/NAT/pxping_win.c	(revision 53367)
+++ /trunk/src/VBox/NetworkServices/NAT/pxping_win.c	(revision 53368)
@@ -475,5 +475,12 @@
     }
 
-    bufsize = sizeof(ICMPV6_ECHO_REPLY) + p->tot_len;
+    /* XXX: parrotted from IPv4 version, not tested all os version/bitness */
+    bufsize = sizeof(ICMPV6_ECHO_REPLY);
+    if (p->tot_len < sizeof(IO_STATUS_BLOCK) + sizeof(struct icmp6_echo_hdr))
+        bufsize += sizeof(IO_STATUS_BLOCK) + sizeof(struct icmp6_echo_hdr);
+    else
+        bufsize += p->tot_len;
+    bufsize += 16;
+
     pong = (struct pong6 *)malloc(RT_OFFSETOF(struct pong6, buf) + bufsize);
     if (RT_UNLIKELY(pong == NULL)) {