An Insecure Permissions vulnerability in SpawningKit in Phusion Passenger 5.3.x before 5.3.2 causes information disclosure in the following situation: given a Passenger-spawned application process that reports that it listens on a certain Unix domain socket, if any of the parent directories of said socket are writable by a normal user that is not the application's user, then that non-application user can swap that directory with something else, resulting in traffic being redirected to a non-application user's process through an alternative Unix domain socket.

References

• https://nvd.nist.gov/vuln/detail/CVE-2018-12027
• https://blog.phusion.nl/passenger-5-3-2
• https://security.gentoo.org/glsa/201807-02
• https://github.com/rubysec/ruby-advisory-db/blob/master/gems/passenger/CVE-2018-12027.yml