ASA-2019-00468 – FreeBSD: pts write-after-free

The code which handles a close(2) of a descriptor created by posix_openpt(2) fails to undo the configuration which causes SIGIO to be raised. This bug can lead to a write-after-free of kernel memory. The bug permits malicious code to trigger a write-after-free, which may be used to gain root privileges or escape a jail.