A race condition in the nginx module in Phusion Passenger 3.x through 5.x before 5.3.2 allows local escalation of privileges when a non-standard passenger_instance_registry_dir with insufficiently strict permissions is configured. Replacing a file with a symlink after the file was created, but before it was chowned, leads to the target of the link being chowned via the path. Targeting sensitive files such as root's crontab file allows privilege escalation.
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
| Link | Tags |
|---|---|
| https://blog.phusion.nl/passenger-5-3-2 | mitigation vendor advisory |
| https://security.gentoo.org/glsa/201807-02 | third party advisory vendor advisory |
| https://pulsesecurity.co.nz/advisories/phusion-passenger-priv-esc | third party advisory |
| https://lists.debian.org/debian-lts-announce/2018/06/msg00007.html | third party advisory mailing list |