https://bugs.gentoo.org/572428
https://lists.gnu.org/archive/html/bug-cpio/2016-01/msg00002.html
http://seclists.org/oss-sec/2016/q1/136

--- a/src/copyin.c
+++ b/src/copyin.c
@@ -1385,6 +1385,8 @@
 	  break;
 	}
 
+      if (file_hdr.c_namesize <= 1)
+	file_hdr.c_name = xrealloc (file_hdr.c_name, 2);
       cpio_safer_name_suffix (file_hdr.c_name, false, !no_abs_paths_flag,
 			      false);
       
