Phusion Passenger before 4.0.37 allows local users to write to certain files and directories via a symlink attack on (1) control_process.pid or a (2) generation-* file.
openwall.com/lists/oss-security/2014/01/28/8
openwall.com/lists/oss-security/2014/01/30/3
bugs.debian.org/cgi-bin/bugreport.cgi?bug=736958
bugzilla.redhat.com/show_bug.cgi?id=1058992
github.com/phusion/passenger/commit/34b1087870c2
lists.fedoraproject.org/pipermail/package-announce/2015-February/149032.html