CVE-2026-68200: ALSA: timer: don't re-enter an instance callback that is still running

Published Aug 10, 2026
·
Updated

In the Linux kernel, the following vulnerability has been resolved:

ALSA: timer: don't re-enter an instance callback that is still running

The userspace-driven timer (utimer) TRIGGER ioctl calls sndtimerinterrupt() directly with no serialization, so two threads triggering the same utimer can run sndtimerinterrupt() on one sndtimer concurrently.

sndtimerprocesscallbacks() drops timer->lock around each instance callback and marks the in-flight callback with the single SNDRVTIMERIFLGCALLBACK bit; sndtimercloselocked() waits on that bit to drain an in-flight callback before freeing the instance. The bit cannot represent two concurrent callbacks: when a second interrupt re-queues an instance whose callback is still running, both run at once, the first to finish clears the bit, and the close-path drain then frees the instance (and its callbackdata) while the other callback is still live - a use-after-free reachable by any user able to open /dev/snd/timer, both via a user timer instance and via a sequencer queue timer bound to the utimer.

sndtimerinterrupt() sets IFLGCALLBACK before dropping timer->lock, so a concurrent interrupt already observes it under the lock. Skip re-queuing an instance (and its slaves) to the ack/sack list while its callback is in flight; the accumulated pticks are delivered on the next tick, so no event is lost.

Affected Software

130 affected componentsFixes available
Linux Kernel
ubuntu/linux-hwe-edge*
ubuntu/linux-aws-5.0*
ubuntu/linux-aws-5.3*
ubuntu/linux-azure*
ubuntu/linux-azure-5.3*
ubuntu/linux-azure-edge*
ubuntu/linux-gcp*
ubuntu/linux-gcp-5.3*
ubuntu/linux-gke-4.15*
ubuntu/linux-gke-5.4*
ubuntu/linux-gkeop-5.4*
ubuntu/linux-hwe*
ubuntu/linux-hwe-edge*
ubuntu/linux-oem*
ubuntu/linux-oracle-5.0*
ubuntu/linux-oracle-5.3*
ubuntu/linux-aws-5.11*
ubuntu/linux-aws-5.13*
ubuntu/linux-aws-5.8*
ubuntu/linux-azure-5.11*
ubuntu/linux-azure-5.13*
ubuntu/linux-azure-5.8*
ubuntu/linux-azure-fde*
ubuntu/linux-gcp-5.11*
ubuntu/linux-gcp-5.13*
ubuntu/linux-gcp-5.8*
ubuntu/linux-gke*
ubuntu/linux-gke-5.15*
ubuntu/linux-gkeop*
ubuntu/linux-gkeop-5.15*
ubuntu/linux-hwe-5.11*
ubuntu/linux-hwe-5.13*
ubuntu/linux-hwe-5.8*
ubuntu/linux-intel-5.13*
ubuntu/linux-oem-5.10*
ubuntu/linux-oem-5.13*
ubuntu/linux-oem-5.6*
ubuntu/linux-oracle-5.11*
ubuntu/linux-oracle-5.13*
ubuntu/linux-oracle-5.8*
ubuntu/linux-raspi2*
ubuntu/linux-riscv*
ubuntu/linux-riscv-5.11*
ubuntu/linux-riscv-5.8*
ubuntu/linux-allwinner-5.19*
ubuntu/linux-aws-5.19*
ubuntu/linux-aws-6.2*
ubuntu/linux-aws-6.5*
ubuntu/linux-azure-5.19*
ubuntu/linux-azure-6.2*
ubuntu/linux-azure-6.5*
ubuntu/linux-azure-fde-5.19*
ubuntu/linux-azure-fde-6.2*
ubuntu/linux-gcp-5.19*
ubuntu/linux-gcp-6.2*
ubuntu/linux-gcp-6.5*
ubuntu/linux-hwe-5.19*
ubuntu/linux-hwe-6.2*
ubuntu/linux-hwe-6.5*
ubuntu/linux-intel-iot-realtime*
ubuntu/linux-lowlatency-hwe-5.19*
ubuntu/linux-lowlatency-hwe-6.2*
ubuntu/linux-lowlatency-hwe-6.5*
ubuntu/linux-nvidia-6.2*
ubuntu/linux-nvidia-6.5*
ubuntu/linux-oem-5.17*
ubuntu/linux-oem-6.0*
ubuntu/linux-oem-6.1*
ubuntu/linux-oem-6.5*
ubuntu/linux-oracle-6.5*
ubuntu/linux-realtime*
ubuntu/linux-riscv*
ubuntu/linux-riscv-5.19*
ubuntu/linux-riscv-6.5*
ubuntu/linux-starfive-5.19*
ubuntu/linux-starfive-6.2*
ubuntu/linux-starfive-6.5*
ubuntu/linux-aws-6.14*
ubuntu/linux-aws-6.17*
ubuntu/linux-aws-7.0<7.0.0-1014.14~24.04.1
7.0.0-1014.14~24.04.1
ubuntu/linux-azure-6.11*
ubuntu/linux-azure-6.14*
ubuntu/linux-azure-6.17*
ubuntu/linux-azure-7.0<7.0.0-1017.17~24.04.1
7.0.0-1017.17~24.04.1
ubuntu/linux-azure-fde-6.14*
ubuntu/linux-azure-fde-6.17*
ubuntu/linux-azure-fde-7.0<7.0.0-1016.16~24.04.1
7.0.0-1016.16~24.04.1
ubuntu/linux-azure-nvidia-6.14*
ubuntu/linux-gcp-6.11*
ubuntu/linux-gcp-6.14*
ubuntu/linux-gcp-7.0<7.0.0-1014.14~24.04.1
7.0.0-1014.14~24.04.1
ubuntu/linux-hwe-6.11*
ubuntu/linux-hwe-6.14*
ubuntu/linux-hwe-6.17*
ubuntu/linux-hwe-7.0<7.0.0-38.38~24.04.4
7.0.0-38.38~24.04.4
ubuntu/linux-lowlatency-hwe-6.11*
ubuntu/linux-nvidia-6.11*
ubuntu/linux-nvidia-6.17*
ubuntu/linux-nvidia-7.0<7.0.0-1024.25~24.04.1
7.0.0-1024.25~24.04.1
ubuntu/linux-oem-6.11*
ubuntu/linux-oem-6.14*
ubuntu/linux-oem-6.17*
ubuntu/linux-oem-6.8*
ubuntu/linux-oracle-6.14*
ubuntu/linux-oracle-6.17*
ubuntu/linux-oracle-7.0<7.0.0-1013.13~24.04.1
7.0.0-1013.13~24.04.1
ubuntu/linux-raspi-realtime*
ubuntu/linux-realtime*
ubuntu/linux-riscv*
ubuntu/linux-riscv-6.14*
ubuntu/linux-riscv-6.17*
ubuntu/linux-riscv-7.0<7.0.0-38.38.1~24.04.1
7.0.0-38.38.1~24.04.1
ubuntu/linux-realtime-6.14*
ubuntu/linux-realtime-6.17*
ubuntu/linux<7.0.0-38.38
7.0.0-38.38
ubuntu/linux-aws<7.0.0-1014.14
7.0.0-1014.14
ubuntu/linux-azure<7.0.0-1017.17
7.0.0-1017.17
ubuntu/linux-azure-fde<7.0.0-1016.16
7.0.0-1016.16
ubuntu/linux-gcp<7.0.0-1014.14
7.0.0-1014.14
ubuntu/linux-gke<7.0.0-1008.9
7.0.0-1008.9
ubuntu/linux-ibm<7.0.0-1015.15
7.0.0-1015.15
ubuntu/linux-nvidia*
ubuntu/linux-nvidia-bos<7.0.0-2022.23
7.0.0-2022.23
ubuntu/linux-oem-7.0<7.0.0-1015.15
7.0.0-1015.15
ubuntu/linux-oracle<7.0.0-1013.13
7.0.0-1013.13
ubuntu/linux-raspi*
ubuntu/linux-realtime<7.0.0-38.38.1
7.0.0-38.38.1
ubuntu/linux-riscv<7.0.0-38.38.1
7.0.0-38.38.1
ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade ubuntu/linux-aws-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14~24.04.1
  2. Upgrade

    Upgrade ubuntu/linux-azure-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1017.17~24.04.1
  3. Upgrade

    Upgrade ubuntu/linux-azure-fde-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1016.16~24.04.1
  4. Upgrade

    Upgrade ubuntu/linux-gcp-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14~24.04.1
  5. Upgrade

    Upgrade ubuntu/linux-hwe-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38~24.04.4
  6. Upgrade

    Upgrade ubuntu/linux-nvidia-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1024.25~24.04.1
  7. Upgrade

    Upgrade ubuntu/linux-oracle-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1013.13~24.04.1
  8. Upgrade

    Upgrade ubuntu/linux-riscv-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38.1~24.04.1
  9. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38
  10. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14
  11. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 7.0.0-1017.17
  12. Upgrade

    Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.

    Fixed in 7.0.0-1016.16
  13. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14
  14. Upgrade

    Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.

    Fixed in 7.0.0-1008.9
  15. Upgrade

    Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.

    Fixed in 7.0.0-1015.15
  16. Upgrade

    Upgrade ubuntu/linux-nvidia-bos to a version that resolves this vulnerability.

    Fixed in 7.0.0-2022.23
  17. Upgrade

    Upgrade ubuntu/linux-oem-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1015.15
  18. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 7.0.0-1013.13
  19. Upgrade

    Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38.1
  20. Upgrade

    Upgrade ubuntu/linux-riscv to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38.1

Event History

Aug 10, 2026
CVE Published
via MITRE·12:00 PM
Data Sourced
via MITRE·12:00 PM
DescriptionSeverity
Data Sourced
via Red Hat·12:23 PM
DescriptionSeverityAffected Software
Data Sourced
via OSV·01:20 PM
DescriptionSeverityAffected Software
Data Sourced
via NVD·01:20 PM
DescriptionSeverity

Frequently Asked Questions

1

What is the severity of CVE-2026-68200?

CVE-2026-68200 has a risk score of 53, indicating a medium severity vulnerability.

2

How do I fix CVE-2026-68200?

To fix CVE-2026-68200, update your Linux kernel to the patched version provided by your distribution.

3

What type of vulnerability is CVE-2026-68200?

CVE-2026-68200 is classified as a Use After Free vulnerability in the ALSA subsystem.

4

What impact does CVE-2026-68200 have on systems?

CVE-2026-68200 can allow concurrent threads to trigger a callback leading to potential system instability or crashes.

5

When was CVE-2026-68200 published?

CVE-2026-68200 was published on August 10, 2026.

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