Privilege Escalation Vulnerability in FreeBSD Kqueue

CVE-2026-58099

What is CVE-2026-58099?

A vulnerability exists in the Kqueue implementation in FreeBSD, wherein the process of copying knotes from a parent kqueue to a child fails to properly exclude certain internal marker knotes. This oversight permits a race condition that may allow an unprivileged local user to exploit the situation, potentially escalating their privileges. The lack of adequate memory management when the kqueue lock is released allows another thread to free a marker knote, leading to unintended memory access during an in-flux decrement operation. Users of affected FreeBSD versions should implement the latest security updates to mitigate this risk.

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