# CVE-2026-89543: sunrpc: fix use-after-free in __rpc_clnt_handle_event and __rpc_clnt_remove_pipedir

> A use-after-free in the Linux kernel's sunrpc module allows local attackers to potentially execute code or escalate privileges via stale pipefs pointers.

- **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:** 11 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-100283, BELL-CVE-2026-89543, DEBIAN-CVE-2026-89543, GHSA-892h-jc8g-4jrg, UBUNTU-CVE-2026-89543

## What is CVE-2026-89543?

CVE-2026-89543 is an 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: fix use-after-free in __rpc_clnt_handle_event and __rpc_clnt_remove_pipedir

Normal client creation goes through rpc_setup_pipedir(), which records
clnt->pipefs_sb, but the mount-event path in __rpc_clnt_handle_event()
calls rpc_setup_pipedir_sb() directly and never refreshes that field.
The umount path also removes the directory without clearing
clnt->pipefs_sb.

After a late pipefs mount or any remount, rpc_clnt_remove_pipedir()
compares the current superblock against a stale pipefs_sb pointer and
skips cleanup, leaving pipefs dentries whose inode private data still
points at a freed rpc_clnt, leading to a potential use-after-free during
subsequent rpc_info_open() or rpc_show_info() calls.

Fix this by properly updating clnt->pipefs_sb upon mount events and
clearing it during unmount or failure paths.

## Which versions are affected by CVE-2026-89543?


## How do I fix CVE-2026-89543?

Apply the vendor's patch.

## Is CVE-2026-89543 being exploited?

There is no known exploitation of CVE-2026-89543 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89543 and fix it if it is affected.

What it is: CVE-2026-89543 is an 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-2026-89543 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-2026-89543/ (Markdown: https://insights.sbomify.com/CVE-2026-89543/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89543
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89543
- OSV: https://osv.dev/vulnerability/CVE-2026-89543

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89543/
Summaries are generated and may contain mistakes; the official description above is the record.