Server-Side Request Forgery in ftp-srv

Background

The FTP protocol creates two connections, one for commands and one for transferring data. This second data connection can be created in two ways, on the server by sending the PASV command, or on the client by sending the PORT command.

The PORT command sends the IP and port for the server to connect to the client with.

Issue

Since the client can send an arbitrary IP with the PORT command, this can be used to cause the server to make a connection elsewhere.

Patches

• fix: disallow PORT connections to alternate hosts: e449e75219d918c400dec65b4b0759f60476abca

Deprecation notices have been published for older versions.

Workarounds

Blacklisting the FTP Command PORT will prevent the server from exposing this behaviour through active connections until a fix is applied.

const ftp = new FtpSrv({
  blacklist: ['PORT']
});

References

https://www.npmjs.com/advisories/1445

Credits

Thank you to; @trs for fixing it @andreeleuterio for reporting it to us for an anonymous user (Vincent) through the NPM platform @quiquelhappy for bringing it to our attention after it slipped through the cracks during Christmas

For more information

If you have any questions or comments about this advisory:

• Open an issue at https://github.com/autovance/ftp-srv
• Email us directly; [email protected]