OpenBSD 2.9 through 3.1 allows local users to cause a denial of service (resource exhaustion) and gain root privileges by filling the kernel's file descriptor table and closing file descriptors 0, 1, or 2 before executing a privileged process, which is not properly handled when OpenBSD fails to open an alternate descriptor.
http://www.securityfocus.com/bid/4708
http://www.openbsd.org/errata.html#fdalloc2
http://www.kb.cert.org/vuls/id/314963