CVE-2026-74503 Linux CVE debrief

Who should care

Linux system administrators, kernel developers, and users with access to /dev/snd/timer and /dev/snd/seq should assess their exposure and apply patches or mitigations as necessary.

Why it matters

This vulnerability allows an unprivileged user to potentially escalate privileges or cause system instability. Linux system administrators and users with access to /dev/snd/timer and /dev/snd/seq should assess their exposure and apply patches or mitigations as necessary.

• Potential privilege escalation from unprivileged user to root
• System crashes or instability due to use-after-free conditions
• Increased risk of exploitation through /dev/snd/timer and /dev/snd/seq

Technical summary

The Linux kernel's ALSA timer functionality has a use-after-free vulnerability. When a timer instance is closed, it is marked with SNDRV_TIMER_IFLG_DEAD but not properly cleared. An unprivileged user can reopen the instance, leading to a use-after-free condition. This can cause a system crash or potentially allow for privilege escalation. The vulnerability exists due to the improper handling of the SNDRV_TIMER_IFLG_DEAD flag in the snd_timer_close_locked function. An attacker can exploit this by reopening a timer instance after it has been closed, leading to a use-after-free condition.

Defensive priority

High

Recommended defensive actions

• Review and apply the provided patches to the Linux kernel
• Restrict access to /dev/snd/timer and /dev/snd/seq to privileged users only
• Monitor system logs for potential exploitation attempts
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The vulnerability exists in the Linux kernel's ALSA timer functionality. An unprivileged user can trigger a use-after-free condition by reopening a timer instance after it has been closed. This can lead to a crash or potentially allow for privilege escalation.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.