Use-after-free in kqueue copy-on-fork

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-58083
StatePUBLISHED
Assignerfreebsd
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-19 08:17:12 UTC
Updated2026-08-31 19:02:30 UTC
DescriptionWhile 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.

Risk And Classification

Primary CVSS: v3.1 8.4 HIGH from ADP

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.001230000 probability, percentile 0.023220000 (date 2026-09-01)

Problem Types: CWE-416 | CWE-416 CWE-416: Use After Free

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED8.4HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary8.4HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Freebsd Freebsd 15.1 - All All
Operating System Freebsd Freebsd 15.1 p1 All All
Operating System Freebsd Freebsd 15.1 rc2 All All
Operating System Freebsd Freebsd 15.1 rc3-p1 All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA FreeBSD FreeBSD affected 15.1-RELEASE p2 release Not specified

References

ReferenceSourceLinkTags
security.freebsd.org/advisories/FreeBSD-SA-26:50.kqueue.asc [email protected] security.freebsd.org Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Hazley Samsudin of GovTech CSG (en)

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