CVE-2026-58091 Kernel use-after-free via the SNDCTL_DSP_SYNCSTART ioctl
An unprivileged local user can exploit a use-after-free in the FreeBSD kernel audio driver to escalate privileges.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-58091?
CVE-2026-58091 is a high-severity use after free vulnerability in Freebsd Freebsd, published on 26 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
The implementation of this ioctl attempts to acquire locks on all channels in a sync group. If locking a channel would block, it releases the sync group list lock and sleeps. Upon reawakening, it is possible that the sync group structure is freed, but the implementation did not handle this possibility.
On a system with a multiple audio devices, an unprivileged local user can exploit this use-after-free to escalate privileges.
Weakness: CWE-416
Which versions are affected by CVE-2026-58091?
It affects 1 product.
Products include Freebsd Freebsd.
How do I fix CVE-2026-58091?
No fix has been published for CVE-2026-58091 yet. Limit exposure of the affected software until one is available.
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-2026-58091 being exploited?
There is no known exploitation of CVE-2026-58091 in the wild and no public exploit code.