Fix invalid byte sequence

changelogs/unreleased/security-dos-issue-and-commit-comments-master.yml

@@ -0,0 +1,5 @@
+---
+title: Fix 500 error caused by invalid byte sequences in links
+merge_request:
+author:
+type: security

lib/banzai/filter/relative_link_filter.rb

@@ -172,7 +172,7 @@ module Banzai
       end
 
       def cleaned_file_path(uri)
-        Addressable::URI.unescape(uri.path).delete("\0").chomp("/")
+        Addressable::URI.unescape(uri.path).scrub.delete("\0").chomp("/")
       end
 
       def relative_file_path(uri)

spec/lib/banzai/filter/relative_link_filter_spec.rb

@@ -119,6 +119,11 @@ describe Banzai::Filter::RelativeLinkFilter do
     expect { filter(act) }.not_to raise_error
   end
 
+  it 'does not raise an exception on URIs containing invalid utf-8 byte sequences' do
+    act = link("%FF")
+    expect { filter(act) }.not_to raise_error
+  end
+
   it 'does not raise an exception with a garbled path' do
     act = link("open(/var/tmp/):%20/location%0Afrom:%20/test")
     expect { filter(act) }.not_to raise_error