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CVE-2026-68202

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

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.266, 5.15.217, 6.1.183, 6.6.148, 6.12.101, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in b7feeaca1f53b10df9b4de9eaf611767ca70dc92; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 7478ef94b49bc9789cf1a003deec58b42283dde4; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 9d9be6fc30f384f92c4e1b8ed40bd9d4796b7833; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in fb40d03ed792a8a8bf77aa0ee15df57b0ff78b07; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 24f0cabf173539f048946c8fc221131dc221f277; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 6a10025c7fd09a7d2af37a3ae1da188569fce470; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 31a6163e301d832060f8236f1ed17cbc1ca198df; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 2c4dc0ed50b05cd847a4b34b8cebf0775f19aeb9

  • Linux Linux

    2.6.12

  • KernelLinux

    From 2.6.12 · fixed in 5.10.266; From 5.11.0 · fixed in 5.15.217; From 5.16.0 · fixed in 6.1.183; From 6.2.0 · fixed in 6.6.148; From 6.7.0 · fixed in 6.12.101; From 6.13.0 · fixed in 6.18.42; From 6.19.0 · fixed in 7.1.6

References 8

git.kernel.org