Fix ReDoS vulnerability in multipart parser

tenderlove · tenderlove · commit ee25ab9a7ee9 · 2023-01-17T12:29:57.000-08:00
This commit fixes a ReDoS vulnerability when parsing the Content-Disposition field in multipart attachments Thanks to @ooooooo_q for the patch! [CVE-2022-44571]
diff --git a/lib/rack/multipart.rb b/lib/rack/multipart.rb
@@ -18,7 +18,7 @@ module Multipart
     VALUE = /"(?:\\"|[^"])*"|#{TOKEN}/
     BROKEN = /^#{CONDISP}.*;\s*filename=(#{VALUE})/i
     MULTIPART_CONTENT_TYPE = /Content-Type: (.*)#{EOL}/ni
-    MULTIPART_CONTENT_DISPOSITION = /Content-Disposition:.*;\s*name=(#{VALUE})/ni
+    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{[^ \x00-\x1f\x7f)(><@,;:\\"/\[\]?='*%]}
