{"id":"CVE-2026-68200","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-68200","summary":"ALSA: timer: don't re-enter an instance callback that is still running","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: timer: don't re-enter an instance callback that is still running\n\nThe userspace-driven timer (utimer) TRIGGER ioctl calls\nsnd_timer_interrupt() directly with no serialization, so two threads\ntriggering the same utimer can run snd_timer_interrupt() on one\nsnd_timer concurrently.\n\nsnd_timer_process_callbacks() drops timer->lock around each instance\ncallback and marks the in-flight callback with the single\nSNDRV_TIMER_IFLG_CALLBACK bit; snd_timer_close_locked() waits on that\nbit to drain an in-flight callback before freeing the instance. The bit\ncannot represent two concurrent callbacks: when a second interrupt\nre-queues an instance whose callback is still running, both run at once,\nthe first to finish clears the bit, and the close-path drain then frees\nthe instance (and its callback_data) while the other callback is still\nlive - a use-after-free reachable by any user able to open\n/dev/snd/timer, both via a user timer instance and via a sequencer queue\ntimer bound to the utimer.\n\nsnd_timer_interrupt() sets IFLG_CALLBACK before dropping timer->lock, so\na concurrent interrupt already observes it under the lock. Skip\nre-queuing an instance (and its slaves) to the ack/sack list while its\ncallback is in flight; the accumulated pticks are delivered on the next\ntick, so no event is lost.","published":"2026-08-10T12:00:19.253Z","modified":"2026-08-14T04:04:01.096151585Z","cvss":{"score":7.8,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.12.101"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/1395327a96614885552bae5fbb650e6dd182d49b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/70d28bfcd6224eed75986b3b987b997e59643fa4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/996c24377eea4d4506b7c3ccbbf1e490440b5e0b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c1078130a4cd7e738f4b73afe99b3e68cbfbf884"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68200.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-68200"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-14T04:04:01.096151585Z"}}