diff --git a/fileio.c b/fileio.c
index 03fc4be..2a61a30 100644
--- a/fileio.c
+++ b/fileio.c
@@ -176,6 +176,8 @@ static ZCONST char Far FilenameTooLongTrunc[] =
 #endif
 static ZCONST char Far ExtraFieldTooLong[] =
   "warning:  extra field too long (%d).  Ignoring...\n";
+static ZCONST char Far ExtraFieldCorrupt[] =
+  "warning:  extra field (type: 0x%04x) corrupt.  Continuing...\n";
 
 #ifdef WINDLL
    static ZCONST char Far DiskFullQuery[] =
@@ -2300,7 +2302,13 @@ int do_string(__G__ length, option)   /* return PK-type error code */
               length = length2;
             }
             /* Looks like here is where extra fields are read */
-            getZip64Data(__G__ G.extra_field, length);
+            if (getZip64Data(__G__ G.extra_field, length) != PK_COOL)
+            {
+                Info(slide, 0x401, ((char *)slide,
+                 LoadFarString( ExtraFieldCorrupt), EF_PKSZ64));
+                error = PK_WARN;
+            }
+
 #ifdef UNICODE_SUPPORT
             G.unipath_filename = NULL;
             if (G.UzO.U_flag < 2) {
diff --git a/process.c b/process.c
index be6e006..0d57ab4 100644
--- a/process.c
+++ b/process.c
@@ -1,5 +1,5 @@
 /*
-  Copyright (c) 1990-2009 Info-ZIP.  All rights reserved.
+  Copyright (c) 1990-2014 Info-ZIP.  All rights reserved.
 
   See the accompanying file LICENSE, version 2009-Jan-02 or later
   (the contents of which are also included in unzip.h) for terms of use.
@@ -1894,48 +1894,83 @@ int getZip64Data(__G__ ef_buf, ef_len)
     and a 4-byte version of disk start number.
     Sets both local header and central header fields.  Not terribly clever,
     but it means that this procedure is only called in one place.
+
+    2014-12-05 SMS.
+    Added checks to ensure that enough data are available before calling
+    makeint64() or makelong().  Replaced various sizeof() values with
+    simple ("4" or "8") constants.  (The Zip64 structures do not depend
+    on our variable sizes.)  Error handling is crude, but we should now
+    stay within the buffer.
   ---------------------------------------------------------------------------*/
 
+#define Z64FLGS 0xffff
+#define Z64FLGL 0xffffffff
+
     if (ef_len == 0 || ef_buf == NULL)
         return PK_COOL;
 
     Trace((stderr,"\ngetZip64Data: scanning extra field of length %u\n",
       ef_len));
 
-    while (ef_len >= EB_HEADSIZE) {
+    while (ef_len >= EB_HEADSIZE)
+    {
         eb_id = makeword(EB_ID + ef_buf);
         eb_len = makeword(EB_LEN + ef_buf);
 
-        if (eb_len > (ef_len - EB_HEADSIZE)) {
-            /* discovered some extra field inconsistency! */
+        if (eb_len > (ef_len - EB_HEADSIZE))
+        {
+            /* Extra block length exceeds remaining extra field length. */
             Trace((stderr,
               "getZip64Data: block length %u > rest ef_size %u\n", eb_len,
               ef_len - EB_HEADSIZE));
             break;
         }
-        if (eb_id == EF_PKSZ64) {
 
+        if (eb_id == EF_PKSZ64)
+        {
           int offset = EB_HEADSIZE;
 
-          if (G.crec.ucsize == 0xffffffff || G.lrec.ucsize == 0xffffffff){
-            G.lrec.ucsize = G.crec.ucsize = makeint64(offset + ef_buf);
-            offset += sizeof(G.crec.ucsize);
+          if ((G.crec.ucsize == Z64FLGL) || (G.lrec.ucsize == Z64FLGL))
+          {
+            if (offset+ 8 > ef_len)
+              return PK_ERR;
+
+            G.crec.ucsize = G.lrec.ucsize = makeint64(offset + ef_buf);
+            offset += 8;
           }
-          if (G.crec.csize == 0xffffffff || G.lrec.csize == 0xffffffff){
-            G.csize = G.lrec.csize = G.crec.csize = makeint64(offset + ef_buf);
-            offset += sizeof(G.crec.csize);
+
+          if ((G.crec.csize == Z64FLGL) || (G.lrec.csize == Z64FLGL))
+          {
+            if (offset+ 8 > ef_len)
+              return PK_ERR;
+
+            G.csize = G.crec.csize = G.lrec.csize = makeint64(offset + ef_buf);
+            offset += 8;
           }
-          if (G.crec.relative_offset_local_header == 0xffffffff){
+
+          if (G.crec.relative_offset_local_header == Z64FLGL)
+          {
+            if (offset+ 8 > ef_len)
+              return PK_ERR;
+
             G.crec.relative_offset_local_header = makeint64(offset + ef_buf);
-            offset += sizeof(G.crec.relative_offset_local_header);
+            offset += 8;
           }
-          if (G.crec.disk_number_start == 0xffff){
+
+          if (G.crec.disk_number_start == Z64FLGS)
+          {
+            if (offset+ 4 > ef_len)
+              return PK_ERR;
+
             G.crec.disk_number_start = (zuvl_t)makelong(offset + ef_buf);
-            offset += sizeof(G.crec.disk_number_start);
+            offset += 4;
           }
+#if 0
+          break;                /* Expect only one EF_PKSZ64 block. */
+#endif /* 0 */
         }
 
-        /* Skip this extra field block */
+        /* Skip this extra field block. */
         ef_buf += (eb_len + EB_HEADSIZE);
         ef_len -= (eb_len + EB_HEADSIZE);
     }