CVE-2026-58083: Use-after-free in kqueue copy-on-fork
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.
Event History
Frequently Asked Questions
Who can exploit this issue?
An unprivileged local user can trigger the race condition. Exploitation requires local access to a system using the affected kernel behavior.
What kernel activity is involved in triggering the flaw?
The race occurs while the kernel copies knotes during fork. A knote using a timer-based filter must be able to fire and be placed on the kqueue active list before copying completes.
What is the potential impact of successful exploitation?
The active-list corruption can cause a kernel use-after-free. This may allow a local unprivileged user to escalate privileges.