Prevent infinite loop in CFFParser_parseHeader

src/core/fonts.js

@@ -5628,12 +5628,17 @@ var CFFParser = (function CFFParserClosure() {
     },
     parseHeader: function CFFParser_parseHeader() {
       var bytes = this.bytes;
+      var bytesLength = bytes.length;
       var offset = 0;
 
-      while (bytes[offset] != 1)
+      // Prevent an infinite loop, by checking that the offset is within the
+      // bounds of the bytes array. Necessary in empty, or invalid, font files.
+      while (offset < bytesLength && bytes[offset] !== 1) {
         ++offset;
-
-      if (offset !== 0) {
+      }
+      if (offset >= bytesLength) {
+        error('Invalid CFF header');
+      } else if (offset !== 0) {
         info('cff data is shifted');
         bytes = bytes.subarray(offset);
         this.bytes = bytes;