CVE WatchAug 20, 2026

CVE-2026-58083

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 be

CVSS

8.4

High

EPSS

0.2%

KEV

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Exploit Today

0-100

Published: Aug 19, 2026 · Last modified: Aug 20, 2026 · CWE-416

EPSS · 30d

Not enough EPSS history yet.

Technical 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.

Official references

security.freebsd.orghttps://security.freebsd.org/advisories/FreeBSD-SA-26:50.kqueue.asc

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4.2%

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25.6%

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