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.

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History

Wed, 19 Aug 2026 12:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 8.4, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Wed, 19 Aug 2026 11:00:00 +0000

Type Values Removed Values Added
First Time appeared Freebsd
Freebsd freebsd
Vendors & Products Freebsd
Freebsd freebsd

Wed, 19 Aug 2026 07:45:00 +0000

Type Values Removed Values Added
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.
Title Use-after-free in kqueue copy-on-fork
Weaknesses CWE-416
References

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cve-icon MITRE

Status: PUBLISHED

Assigner: freebsd

Published:

Updated: 2026-08-19T11:57:01.505Z

Reserved: 2026-06-29T01:40:17.498Z

Link: CVE-2026-58083

cve-icon Vulnrichment

Updated: 2026-08-19T11:56:46.032Z

cve-icon NVD

Status : Received

Published: 2026-08-19T08:17:12.470

Modified: 2026-08-19T12:18:33.190

Link: CVE-2026-58083

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-19T19:30:04Z

Weaknesses