# CVE-2025-68186: ring-buffer: Do not warn in ring_buffer_map_get_reader() when reader catches up

> A logic error in the Linux kernel ring buffer triggers unnecessary warnings when the reader catches up, potentially causing system instability or 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:** 16 Dec 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-68186, DEBIAN-CVE-2025-68186, GHSA-fmq6-3hwm-4q94, UBUNTU-CVE-2025-68186

## What is CVE-2025-68186?

CVE-2025-68186 is a denial of service 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:

ring-buffer: Do not warn in ring_buffer_map_get_reader() when reader catches up

The function ring_buffer_map_get_reader() is a bit more strict than the
other get reader functions, and except for certain situations the
rb_get_reader_page() should not return NULL. If it does, it triggers a
warning.

This warning was triggering but after looking at why, it was because
another acceptable situation was happening and it wasn't checked for.

If the reader catches up to the writer and there's still data to be read
on the reader page, then the rb_get_reader_page() will return NULL as
there's no new page to get.

In this situation, the reader page should not be updated and no warning
should trigger.

## Which versions are affected by CVE-2025-68186?


## How do I fix CVE-2025-68186?

Apply the vendor's patch.

## Is CVE-2025-68186 being exploited?

There is no known exploitation of CVE-2025-68186 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-68186 and fix it if it is affected.

What it is: CVE-2025-68186 is a denial of service 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-2025-68186 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-2025-68186/ (Markdown: https://insights.sbomify.com/CVE-2025-68186/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-68186
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-68186
- OSV: https://osv.dev/vulnerability/CVE-2025-68186

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-68186/
Summaries are generated and may contain mistakes; the official description above is the record.