# CVE-2022-49889: ring-buffer: Check for NULL cpu_buffer in ring_buffer_wake_waiters()

> A NULL pointer dereference in the Linux kernel tracing subsystem can cause a system crash when waking waiters on unallocated CPU buffers.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 May 2025
- **Updated:** 23 May 2026
- **Also known as:** DEBIAN-CVE-2022-49889, GHSA-w9wh-q8v9-3rwf, UBUNTU-CVE-2022-49889

## What is CVE-2022-49889?

CVE-2022-49889 is a medium-severity vulnerability in Linux kernel, published on 1 May 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:

ring-buffer: Check for NULL cpu_buffer in ring_buffer_wake_waiters()

On some machines the number of listed CPUs may be bigger than the actual
CPUs that exist. The tracing subsystem allocates a per_cpu directory with
access to the per CPU ring buffer via a cpuX file. But to save space, the
ring buffer will only allocate buffers for online CPUs, even though the
CPU array will be as big as the nr_cpu_ids.

With the addition of waking waiters on the ring buffer when closing the
file, the ring_buffer_wake_waiters() now needs to make sure that the
buffer is allocated (with the irq_work allocated with it) before trying to
wake waiters, as it will cause a NULL pointer dereference.

While debugging this, I added a NULL check for the buffer itself (which is
OK to do), and also NULL pointer checks against buffer->buffers (which is
not fine, and will WARN) as well as making sure the CPU number passed in
is within the nr_cpu_ids (which is also not fine if it isn't).

Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1204705

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2022-49889?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2022-49889?

Apply the vendor's patch.

## Is CVE-2022-49889 being exploited?

There is no known exploitation of CVE-2022-49889 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2022-49889 and fix it if it is affected.

What it is: CVE-2022-49889 is a medium-severity vulnerability in Linux kernel, published on 1 May 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-2022-49889 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2022-49889/ (Markdown: https://insights.sbomify.com/CVE-2022-49889/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-49889
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-49889
- OSV: https://osv.dev/vulnerability/CVE-2022-49889

---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-49889/
Summaries are generated and may contain mistakes; the official description above is the record.