CVE-2026-58083 Use-after-free in kqueue copy-on-fork
An unprivileged local user can trigger a use-after-free in the FreeBSD kernel during fork, potentially leading to privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-58083?
CVE-2026-58083 is a high-severity use after free vulnerability in Freebsd Freebsd, published on 19 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
While the kernel was copying knotes during fork, a knote with a timer-based filter could fire and be enqueued on the kqueue's active list before the copy was complete. The copy routine did not account for this and could enqueue the new knote a second time, corrupting the active list. In addition, the copy routine did not hold the appropriate locks while reading knote state, allowing further races.
An unprivileged local user can trigger a use-after-free in the kernel, potentially leading to privilege escalation.
Weakness: CWE-416
Which versions are affected by CVE-2026-58083?
It affects 1 product.
Products include Freebsd Freebsd.
How do I fix CVE-2026-58083?
No fix has been published for CVE-2026-58083 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-2026-58083 being exploited?
There is no known exploitation of CVE-2026-58083 in the wild and no public exploit code.
Other vulnerabilities in Freebsd Freebsd
Sources
Also known as GHSA-j94h-9p69-vhvm.