DescriptionA 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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
NVD severitymedium (attack range: local)
Debian Bugs921767

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
passenger (PTS)stretch (security), stretch5.0.30-1+deb9u1fixed
bullseye, sid, buster5.0.30-1.1fixed
ruby-passenger (PTS)jessie4.0.53-1vulnerable
jessie (security)4.0.53-1+deb8u1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs

Notes (release-5.3.2)
unimportant as nginx module not built.
Related hardening commits: (release-5.3.2) (release-5.3.3)

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