# CVE-2026-93181: perf/x86/intel/uncore: Fix uncore_box ref/unref ordering

> A race condition in the Linux kernel's Intel uncore performance monitoring driver can cause improper resource teardown, leading to a denial of service.

- **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:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** BELL-CVE-2026-93181, DEBIAN-CVE-2026-93181, GHSA-79f3-6wm5-9qvc, UBUNTU-CVE-2026-93181

## What is CVE-2026-93181?

CVE-2026-93181 is a vulnerability in Linux, published on 17 Sep 2026. 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:

perf/x86/intel/uncore: Fix uncore_box ref/unref ordering

In uncore_event_cpu_online(), uncore_box_ref() was called before
uncore_change_context().  uncore_box_ref() gates on box->cpu >= 0,
but box->cpu is still -1 at that point because uncore_change_context()
has not run yet.  As a result, the box is never initialized on the
first CPU to come online in a die, leaving it permanently
uninitialized in the single-CPU-per-die case.

Thus, box->refcnt is one count below the true value, and in the CPU
offline path, the box will be torn down on the second-to-last CPU.

In uncore_event_cpu_offline(), uncore_box_unref() was called after
uncore_change_context(), so box->cpu is already -1 when the collector
CPU goes offline, which prevents it from tearing down the box.

Fix by swapping the call order in both paths so that
uncore_box_{ref,unref}() runs at the point where box->cpu reflects
the correct context.

Move allocate_boxes() out of uncore_box_ref() to enable this
reordering.

## Which versions are affected by CVE-2026-93181?


## How do I fix CVE-2026-93181?

Apply the vendor's patch.

## Is CVE-2026-93181 being exploited?

There is no known exploitation of CVE-2026-93181 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93181 and fix it if it is affected.

What it is: CVE-2026-93181 is a vulnerability in Linux, published on 17 Sep 2026. 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-2026-93181 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-2026-93181/ (Markdown: https://insights.sbomify.com/CVE-2026-93181/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93181
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93181
- OSV: https://osv.dev/vulnerability/CVE-2026-93181

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93181/
Summaries are generated and may contain mistakes; the official description above is the record.