# CVE-2026-89548: SUNRPC: always drain cache_cleaner before destroying a cache_detail

> A use-after-free in the Linux kernel SUNRPC subsystem allows attackers to execute arbitrary code or escalate privileges during network namespace teardown.

- **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:** AZL-100743, BELL-CVE-2026-89548, DEBIAN-CVE-2026-89548, GHSA-3g7j-4hj7-8rgc, UBUNTU-CVE-2026-89548

## What is CVE-2026-89548?

CVE-2026-89548 is a high-severity use after free 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:

SUNRPC: always drain cache_cleaner before destroying a cache_detail

sunrpc_destroy_cache_detail() only cancels the global cache_cleaner
delayed_work when cache_list is empty.  During per-netns teardown
cache_list is never empty because init_net's caches remain registered,
so the cancel never fires.  After unlink, the caller proceeds to
cache_destroy_net() which kfrees the cache_detail while cache_clean()
may still hold a dangling pointer to it.  The result is a
use-after-free: cache_dequeue() takes cd->queue_lock on freed memory,
and cache_put() dereferences cd->cache_put as a function pointer from
freed slab.

Drop the list_empty guard so that cancel_delayed_work_sync() always
runs, ensuring any in-flight cache_clean() completes before the
cache_detail is freed.  Re-arm the cleaner afterwards if other caches
are still registered.

## Which versions are affected by CVE-2026-89548?


## How do I fix CVE-2026-89548?

Apply the vendor's patch.

## Is CVE-2026-89548 being exploited?

There is no known exploitation of CVE-2026-89548 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89548 and fix it if it is affected.

What it is: CVE-2026-89548 is a high-severity use after free 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-2026-89548 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-2026-89548/ (Markdown: https://insights.sbomify.com/CVE-2026-89548/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89548
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89548
- OSV: https://osv.dev/vulnerability/CVE-2026-89548

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89548/
Summaries are generated and may contain mistakes; the official description above is the record.