Information disclosure in Phusion Passenger - CVE-2018-12027

Detailed vulnerability description

The vulnerability allows a local attacker to obtain potentially sensitive information.

The vulnerability exists due to insufficient security restrictions imposed on the SpawningKit subsystem. When an application process that is managed by the affected software reports that it is listening on a certain UNIX domain socket, and the parent directories of the application socket are writable by users other than the user of the application, a local attacker can swap a directory with attacker-controlled contents, redirect traffic to an attacker-controlled process via an alternative, attacker-controlled UNIX domain socket and use it to access sensitive information. 

How to mitigate CVE-2018-12027

Sources

• https://blog.phusion.nl/2018/06/12/passenger-5-3-2-various-security-fixes/