CVE-2019-5596

En FreeBSD 11.2-STABLE tras r338618 y antes de r343786, 12.0-STABLE antes de r343781 y 12.0-RELEASE antes de 12.0-RELEASE-p3, un error en la implementación del conteo de referencias para los sockets del dominio UNIX pueden provocar que se lance incorrectamente una estructura de datos. Esto podría permitir que un usuario local malicioso obtenga privilegios root o escape de una cárcel.

FreeBSD 12.0 attempts to handle the case where the receiving process does not provide a sufficiently large buffer for an incoming control message containing rights. In particular, to avoid leaking the corresponding descriptors into the receiving process' descriptor table, the kernel handles the truncation case by closing descriptors referenced by the discarded message. The code which performs this operation failed to release a reference obtained on the file corresponding to a received right. This bug can be used to cause the reference counter to wrap around and free the file structure. A local user can exploit the bug to gain root privileges or escape from a jail.