---
id: "CVE-2026-98972"
kind: "vulnerability"
aliases: ["CVE-2026-98972"]
title: "Linux kernel: cpuset v2 mode check may read a stale cgroup pointer"
severity: "unknown"
cvss: null
epss: 0.00198
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["containers", "infrastructure", "linux-kernel", "self-hosted"]
not_affected_if: []
published_at: "2026-10-23T13:17:18+00:00"
first_seen_at: "2026-10-23T21:57:33+00:00"
updated_at: "2026-10-25T12:38:50+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98972", "first_seen_at": "2026-10-23T21:57:33+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-98972", "first_seen_at": "2026-10-25T12:38:50+00:00"}]
---

# Linux kernel: cpuset v2 mode check may read a stale cgroup pointer

In the Linux kernel cpuset controller, the is_in_v2_mode() helper could read a cgroup root pointer that is stale while a cgroup filesystem is being rebound. The fix replaces that read with a dedicated cpuset_v2_mode flag, which avoids a potential use-after-free; the sources do not state a direct attacker outcome.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- Update the Linux kernel to a release that includes the upstream commit resolving CVE-2026-98972 (cgroup/cpuset: Don't access cpuset_cgrp_subsys.root in is_in_v2_mode()); the fixed version numbers are not given in the sources.

## Timeline

- 2026-10-23T21:57:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98972
- 2026-10-25T12:38:50+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-98972

## From the sources

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 seeing the patch [1] to guard is_in_v2_mode() with RCU, it makes
me realize that is_in_v2_mode() may be called in a context where a new
cgroup filesystem is being rebound with stale cpuset_cgrp_subsys.root
pointer. Avoid this potential UaF situation by adding a new cpuset_v2_mode
flag which is set when the cpuset_v2_mode mount option is used. This
flag is written into only when cpuset_bind() is being called with a
stable cpuset_cgrp_subsys.root value. The is_in_v2_mode() helper is
modified to read the new cpuset_v2_mode flag instead of accessing
cpuset_cgrp_subsys.root directly.

[1] https://lore.kernel.org/lkml/20260929084124.626693-2-arighi@nvidia.com

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_