# CVE-2025-40346: arch_topology: Fix incorrect error check in topology_parse_cpu_capacity()

> A null pointer dereference in the Linux kernel's CPU topology parsing can cause a system crash, requiring a kernel patch to fix.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Dec 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-40346, DEBIAN-CVE-2025-40346, GHSA-3qw8-vgp2-684r, ROOT-OS-UBUNTU-2404-CVE-2025-40346, UBUNTU-CVE-2025-40346

## What is CVE-2025-40346?

CVE-2025-40346 is a vulnerability in Linux, published on 16 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

arch_topology: Fix incorrect error check in topology_parse_cpu_capacity()

Fix incorrect use of PTR_ERR_OR_ZERO() in topology_parse_cpu_capacity()
which causes the code to proceed with NULL clock pointers. The current
logic uses !PTR_ERR_OR_ZERO(cpu_clk) which evaluates to true for both
valid pointers and NULL, leading to potential NULL pointer dereference
in clk_get_rate().

Per include/linux/err.h documentation, PTR_ERR_OR_ZERO(ptr) returns:
"The error code within @ptr if it is an error pointer; 0 otherwise."

This means PTR_ERR_OR_ZERO() returns 0 for both valid pointers AND NULL
pointers. Therefore !PTR_ERR_OR_ZERO(cpu_clk) evaluates to true (proceed)
when cpu_clk is either valid or NULL, causing clk_get_rate(NULL) to be
called when of_clk_get() returns NULL.

Replace with !IS_ERR_OR_NULL(cpu_clk) which only proceeds for valid
pointers, preventing potential NULL pointer dereference in clk_get_rate().

## Which versions are affected by CVE-2025-40346?


## How do I fix CVE-2025-40346?

Apply the vendor's patch.

## Is CVE-2025-40346 being exploited?

There is no known exploitation of CVE-2025-40346 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40346 and fix it if it is affected.

What it is: CVE-2025-40346 is a vulnerability in Linux, published on 16 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-40346 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-40346/ (Markdown: https://insights.sbomify.com/CVE-2025-40346/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40346
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40346
- OSV: https://osv.dev/vulnerability/CVE-2025-40346

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40346/
Summaries are generated and may contain mistakes; the official description above is the record.