# CVE-2026-68202: ALSA: seq: close a re-opened queue timer in the destructor

> An unprivileged user can trigger a use-after-free in the ALSA sequencer timer destructor, potentially leading to code execution or privilege escalation.

- **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:** 10 Aug 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-68202, DEBIAN-CVE-2026-68202, GHSA-62fv-xj62-4r9q, UBUNTU-CVE-2026-68202

## What is CVE-2026-68202?

CVE-2026-68202 is a high-severity use after free vulnerability in Linux, published on 10 Aug 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:

ALSA: seq: close a re-opened queue timer in the destructor

queue_delete() closes the queue timer, then frees it. snd_seq_timer_close()
clears q->timer->timeri. snd_use_lock_sync() then drains borrowers, and
snd_seq_timer_delete() frees q->timer.

A borrower can re-open the timer inside that window. A SET_QUEUE_CLIENT
that took a queueptr() use_lock reference before the queue was unlinked
runs snd_seq_timer_open() after the close. Open refuses re-open only while
timeri is set, and the close just cleared it, so it re-opens timeri.

snd_seq_timer_delete() does not close that instance. Its snd_seq_timer_stop()
is a no-op, because running was cleared first. So it frees q->timer with the
instance still live. The queue is freed next.

The instance stays on the global timer with callback_data pointing at the
freed queue. A non-owner START on the unlocked queue arms it. The next tick
derefs the freed queue in snd_seq_timer_interrupt().

Reachable by an unprivileged user with access to /dev/snd/seq. No CAP and
no queue ownership required.

Close any lingering instance in the destructor. There, ->timeri can no
longer change: the queue is unlinked and all use_lock borrowers have
drained, so no snd_seq_queue_use() can re-open it. Close it before clearing
q->timer. snd_timer_close() waits for any in-flight snd_seq_timer_interrupt()
to finish, and that callback still reads q->timer (via snd_seq_check_queue()),
so q->timer must stay valid until it drains.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-68202?


## How do I fix CVE-2026-68202?

Apply the vendor's patch.

## Is CVE-2026-68202 being exploited?

There is no known exploitation of CVE-2026-68202 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68202 and fix it if it is affected.

What it is: CVE-2026-68202 is a high-severity use after free vulnerability in Linux, published on 10 Aug 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-2026-68202 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-2026-68202/ (Markdown: https://insights.sbomify.com/CVE-2026-68202/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68202
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68202
- OSV: https://osv.dev/vulnerability/CVE-2026-68202

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68202/
Summaries are generated and may contain mistakes; the official description above is the record.