net/ipv4/route.c in the Linux kernel 4.13-rc1 through 4.13-rc6 is too late to check for a NULL fi field when RTM_F_FIB_MATCH is set, which allows local users to cause a denial of service (NULL pointer dereference) or possibly have unspecified other impact via crafted system calls. NOTE: this does not affect any stable release. Upstream patch: https://github.com/torvalds/linux/commit/bc3aae2bbac46dd894c89db5d5e98f7f0ef9e205