Vulnerability in netfilter code allows local privilege escalation

Many high-level technologies in the IT industry, in fact most of them, are built on top of existing features. Containers are a prime example of this. This lightweight virtualization layer is built on top of a foundation that, among other things, relies heavily on cgroups. Cgroups, aka control groups, are an abstraction that allows specific system components like memory, CPU, or networking to be separated by access levels. This is useful for hiding parts of the system from specific processes running on it, enabling some processes to run “isolated” from the rest of the system or “inside a container”.

But this layering of technologies brings some risks. When a vulnerability that affects one of the foundation components appears, the whole stack is potentially vulnerable. This is what happened with CVE-2022-25636, a recently divulged vulnerability that affects the cgroups’ networking code. It impacts distributions running Kernel 4.18.0-240.el8 and above (RHEL 8 and derivatives like AlmaLinux 8, CentOS 8, Oracle EL 8, as well as Ubuntu and others). It allows privilege escalation for local users. KernelCare Enterprise patches will be made available soon and this post will be updated to reflect such availability as it happens.

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