CVE-2023-4206: Use-after-free in Linux kernel's net/sched: cls_route component

A use-after-free vulnerability in the Linux kernel's net/sched: clsroute component can be exploited to achieve local privilege escalation.

When route4change() is called on an existing filter, the whole tcfresult struct is always copied into the new instance of the filter. This causes a problem when updating a filter bound to a class, as tcfunbindfilter() is always called on the old instance in the success path, decreasing filtercnt of the still referenced class and allowing it to be deleted, leading to a use-after-free.

We recommend upgrading past commit b80b829e9e2c1b3f7aae34855e04d8f6ecaf13c8.

— MITRE

Linux Kernel could allow a local authenticated attacker to gain elevated privileges on the system, caused by a use-after-free flaw in the net/sched: clsroute component. By sending a specially crafted request, an authenticated attacker could exploit this vulnerability to gain elevated privileges.

— IBM