In the Linux kernel, the following vulnerability has been resolved: cgroup/cpuset: Don't access cpuset_cgrp_subsys.root in is_in_v2_mode() After… (CVE-2026-98972)

The vulnerability in the Linux kernel's cgroup cpuset subsystem involved the is_in_v2_mode() function accessing cpuset_cgrp_subsys.root directly, which could be stale during certain operations such as rebinding the cgroup filesystem. This could lead to a use-after-free condition. The patch replaces this direct access with a new cpuset_v2_mode flag that is set only when the cpuset_v2_mode mount option is used and is updated safely during cpuset_bind() calls with a stable root pointer. This change prevents the use-after-free scenario by avoiding dereferencing a potentially invalid pointer.

The vulnerability could cause a use-after-free condition in the kernel, potentially leading to kernel crashes or undefined behavior. However, no known exploits in the wild have been reported. The impact is limited to kernel stability and security related to cgroup cpuset management.

A patch has been applied to the Linux kernel to fix this vulnerability by introducing a safe flag for cpuset v2 mode and avoiding unsafe pointer dereferences. Users should update to the fixed kernel version once available. No additional mitigation is indicated by the vendor advisory.