# CVE-2026-89536: SUNRPC: wait for in-flight client TLS handshake callback

> A race condition in the Linux kernel SUNRPC TLS handshake allows a use-after-free, potentially causing system crashes or arbitrary code execution.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100475, BELL-CVE-2026-89536, DEBIAN-CVE-2026-89536, GHSA-fhrg-h295-8p3m, UBUNTU-CVE-2026-89536

## What is CVE-2026-89536?

CVE-2026-89536 is a critical use after free vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

SUNRPC: wait for in-flight client TLS handshake callback

xs_tls_handshake_sync() gives xs_tls_handshake_done() a reference to the
lower transport before submitting the handshake request. On timeout or
signal, the synchronous waiter drops that reference after calling
tls_handshake_cancel().

handshake_req_cancel() returns false when handshake_complete() has
already marked the request complete. In that case the completion callback
can still be running, so dropping the callback-owned reference in the
waiter can free the lower transport before xs_tls_handshake_done() stores
xprt_err or drops its own reference.

If cancellation loses to completion, wait until xs_tls_handshake_done()
signals handshake_done and let the callback release its reference. This
mirrors the server-side handshake lifetime handling and keeps the timeout
or signal return value unchanged.

## Which versions are affected by CVE-2026-89536?


## How do I fix CVE-2026-89536?

Apply the vendor's patch.

## Is CVE-2026-89536 being exploited?

There is no known exploitation of CVE-2026-89536 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89536 and fix it if it is affected.

What it is: CVE-2026-89536 is a critical use after free vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-89536 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-2026-89536/ (Markdown: https://insights.sbomify.com/CVE-2026-89536/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89536
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89536
- OSV: https://osv.dev/vulnerability/CVE-2026-89536

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89536/
Summaries are generated and may contain mistakes; the official description above is the record.