diff --git a/hw/net/e1000.c b/hw/net/e1000.c
index 5c6bcd0..09c9e9d 100644
--- a/hw/net/e1000.c
+++ b/hw/net/e1000.c
@@ -740,7 +740,8 @@
                 memmove(tp->data, tp->header, tp->hdr_len);
                 tp->size = tp->hdr_len;
             }
-        } while (split_size -= bytes);
+            split_size -= bytes;
+        } while (bytes && split_size);
     } else if (!tp->tse && tp->cptse) {
         // context descriptor TSE is not set, while data descriptor TSE is set
         DBGOUT(TXERR, "TCP segmentation error\n");
diff --git a/hw/net/ne2000.c b/hw/net/ne2000.c
index 53c704a..010f9ef 100644
--- a/hw/net/ne2000.c
+++ b/hw/net/ne2000.c
@@ -221,6 +221,9 @@
     }
 
     index = s->curpag << 8;
+    if (index >= NE2000_PMEM_END) {
+        index = s->start;
+    }
     /* 4 bytes for header */
     total_len = size + 4;
     /* address for next packet (4 bytes for CRC) */
@@ -244,7 +247,7 @@
         if (index <= s->stop)
             avail = s->stop - index;
         else
-            avail = 0;
+            break;
         len = size;
         if (len > avail)
             len = avail;
@@ -306,13 +309,19 @@
         offset = addr | (page << 4);
         switch(offset) {
         case EN0_STARTPG:
-            s->start = val << 8;
+            if (val << 8 <= NE2000_PMEM_END) {
+                s->start = val << 8;
+            }
             break;
         case EN0_STOPPG:
-            s->stop = val << 8;
+            if (val << 8 <= NE2000_PMEM_END) {
+                s->stop = val << 8;
+            }
             break;
         case EN0_BOUNDARY:
-            s->boundary = val;
+            if (val << 8 < NE2000_PMEM_END) {
+                s->boundary = val;
+            }
             break;
         case EN0_IMR:
             s->imr = val;
@@ -353,7 +362,9 @@
             s->phys[offset - EN1_PHYS] = val;
             break;
         case EN1_CURPAG:
-            s->curpag = val;
+            if (val << 8 < NE2000_PMEM_END) {
+                s->curpag = val;
+            }
             break;
         case EN1_MULT ... EN1_MULT + 7:
             s->mult[offset - EN1_MULT] = val;