Index: /trunk/src/VBox/Devices/Network/slirp/slirp.c
===================================================================
--- /trunk/src/VBox/Devices/Network/slirp/slirp.c	(revision 53337)
+++ /trunk/src/VBox/Devices/Network/slirp/slirp.c	(revision 53338)
@@ -1449,4 +1449,6 @@
 
     M_ASSERTPKTHDR(m);
+
+    Assert(M_LEADINGSPACE(m) >= ETH_HLEN);
     m->m_data -= ETH_HLEN;
     m->m_len += ETH_HLEN;