# CVE-2026-89771: ring-buffer: Fix subbuf resize race with ring buffer readers

> A race condition in the Linux kernel ring buffer allows concurrent resizing and reading, potentially causing system instability or crashes.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-89771, DEBIAN-CVE-2026-89771, GHSA-8mw5-wv48-mphh, UBUNTU-CVE-2026-89771

## What is CVE-2026-89771?

CVE-2026-89771 is a high-severity vulnerability in Linux, published on 11 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:

ring-buffer: Fix subbuf resize race with ring buffer readers

trace_buffer subbuf_size is read lockless in ring_buffer_read_page() and
ring_buffer_read_start(), while it can simultaneously be resized with
ring_buffer_subbuf_order_set().

Instead of trace_buffer::subbuf_size, use bpage::order in
ring_buffer_read_start() and ring_buffer_read_page().

In ring_buffer_read_start(), even with resize_disabled, there is still a
possibility of a race with a buffer modification. Hold the trace_buffer
mutex to synchronise with any pending ring buffer order modification.

trace_buffer::subbuf_size is now actually useless, remove it. Also,
create accessors rb_subbuf_capacity() and rb_page_capacity() which
return the actual size available for storing events, while
rb_subbuf_size() returns the actual subbuf page-size.

## Which versions are affected by CVE-2026-89771?


## How do I fix CVE-2026-89771?

Apply the vendor's patch.

## Is CVE-2026-89771 being exploited?

There is no known exploitation of CVE-2026-89771 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89771 and fix it if it is affected.

What it is: CVE-2026-89771 is a high-severity vulnerability in Linux, published on 11 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-2026-89771 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-2026-89771/ (Markdown: https://insights.sbomify.com/CVE-2026-89771/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89771
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89771
- OSV: https://osv.dev/vulnerability/CVE-2026-89771

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89771/
Summaries are generated and may contain mistakes; the official description above is the record.