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.
- 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
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
Which versions are affected by CVE-2026-68202?
How do I fix CVE-2026-68202?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-68202 being exploited?
There is no known exploitation of CVE-2026-68202 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-68202, DEBIAN-CVE-2026-68202, GHSA-62fv-xj62-4r9q, UBUNTU-CVE-2026-68202.