# CVE-2026-72221: sunrpc: wait for in-flight TLS handshake callback when cancel loses race

> A race condition in the Linux kernel's sunrpc TLS handshake handling can corrupt internal state, potentially leading to a denial of service.

- **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:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-72221, DEBIAN-CVE-2026-72221, GHSA-5gf3-c25p-fm95, UBUNTU-CVE-2026-72221

## What is CVE-2026-72221?

CVE-2026-72221 is a critical vulnerability in Linux, published on 15 Aug 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 TLS handshake callback when cancel loses race

When wait_for_completion_interruptible_timeout() in
svc_tcp_handshake() returns 0 (timeout) or -ERESTARTSYS (signal) and
tls_handshake_cancel() then returns false, handshake_complete() has
won the cancellation race: it has set HANDSHAKE_F_REQ_COMPLETED and
is about to invoke svc_tcp_handshake_done(), but the callback's
side effects on xpt_flags and on svsk->sk_handshake_done have not
yet committed.

The current code reads xpt_flags immediately to decide whether the
session succeeded. Two races result.

If the callback has executed set_bit(XPT_TLS_SESSION) but not yet
clear_bit(XPT_HANDSHAKE), svc_tcp_handshake() sees a session,
enqueues the transport, and returns. svc_xprt_received() then
clears XPT_BUSY, a worker thread picks the transport up, the
dispatcher in svc_handle_xprt() observes XPT_HANDSHAKE still set,
and xpo_handshake is invoked a second time. That svc_tcp_handshake()
calls init_completion(&svsk->sk_handshake_done) while the original
callback concurrently calls complete_all() on it, corrupting the
embedded swait_queue.

If the callback has set HANDSHAKE_F_REQ_COMPLETED but not yet
entered svc_tcp_handshake_done(), svc_tcp_handshake() reads
XPT_TLS_SESSION as clear and tears the connection down even though
the handshake is about to succeed.

Wait for the callback to commit before inspecting xpt_flags. The
completion is guaranteed to fire because handshake_complete()
invokes svc_tcp_handshake_done() unconditionally once it has set
HANDSHAKE_F_REQ_COMPLETED.

## Which versions are affected by CVE-2026-72221?


## How do I fix CVE-2026-72221?

Apply the vendor's patch.

## Is CVE-2026-72221 being exploited?

There is no known exploitation of CVE-2026-72221 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72221 and fix it if it is affected.

What it is: CVE-2026-72221 is a critical vulnerability in Linux, published on 15 Aug 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-2026-72221 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-2026-72221/ (Markdown: https://insights.sbomify.com/CVE-2026-72221/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72221
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72221
- OSV: https://osv.dev/vulnerability/CVE-2026-72221

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72221/
Summaries are generated and may contain mistakes; the official description above is the record.