This patch restricts the characters accepted in ATTRIBUTE_CHAR,
forbidding control characters and fixing a ReDOS vulnerability.
--- a/lib/rack/multipart.rb
+++ b/lib/rack/multipart.rb
@@ -21,7 +21,7 @@
     MULTIPART_CONTENT_DISPOSITION = /Content-Disposition:[^:]*;\s*name=(#{VALUE})/ni
     MULTIPART_CONTENT_ID = /Content-ID:\s*([^#{EOL}]*)/ni
     # Updated definitions from RFC 2231
-    ATTRIBUTE_CHAR = %r{[^ \t\v\n\r)(><@,;:\\"/\[\]?='*%]}
+    ATTRIBUTE_CHAR = %r{[^ \x00-\x1f\x7f)(><@,;:\\"/\[\]?='*%]}
     ATTRIBUTE = /#{ATTRIBUTE_CHAR}+/
     SECTION = /\*[0-9]+/
     REGULAR_PARAMETER_NAME = /#{ATTRIBUTE}#{SECTION}?/