diff -urp Mail-SpamAssassin-3.4.2/lib/Mail/SpamAssassin/Message.pm Mail-SpamAssassin-3.4.2.new/lib/Mail/SpamAssassin/Message.pm
--- Mail-SpamAssassin-3.4.2/lib/Mail/SpamAssassin/Message.pm	2018-09-14 03:27:51.000000000 +0200
+++ Mail-SpamAssassin-3.4.2.new/lib/Mail/SpamAssassin/Message.pm	2020-04-09 15:17:34.300986337 +0200
@@ -876,6 +876,7 @@ sub _parse_multipart {
   my $header;
   my $part_array;
   my $found_end_boundary;
+  my $partcnt = 0;
 
   my $line_count = @{$body};
   foreach ( @{$body} ) {
@@ -948,6 +949,13 @@ sub _parse_multipart {
 	}
       }
 
+      # Maximum parts to process
+      if (++$partcnt == 1000) {
+        dbg("message: mimepart limit exceeded, stopping parsing");
+        $self->{'mimepart_limit_exceeded'} = 1;
+        return;
+      }
+
       # make sure we start with a new clean node
       $in_body  = 0;
       $part_msg = Mail::SpamAssassin::Message::Node->new({ normalize=>$self->{normalize} });