The timercreate syscall implementation in kernel/time/posix-timers.c in the Linux kernel before 4.14.8 doesn't properly validate the sigevent->sigevnotify field, which leads to out-of-bounds access in the showtimer function (called when /proc/$PID/timers is read). This allows userspace applications to read arbitrary kernel memory (on a kernel built with CONFIGPOSIXTIMERS and CONFIGCHECKPOINT_RESTORE).