FreeBSD : FreeBSD -- Use-after-free in kqueue copy-on-fork (a4e4a74c-8bb7-11f1-a6ab-bc241121aa0a)

high Nessus Plugin ID 330812

Synopsis

The remote FreeBSD host is missing one or more security-related updates.

Description

The version of FreeBSD installed on the remote host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the a4e4a74c-8bb7-11f1-a6ab-bc241121aa0a advisory.

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.

Tenable has extracted the preceding description block directly from the FreeBSD security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Update the affected packages.

Plugin Details

Severity: High

ID: 330812

File Name: freebsd_pkg_a4e4a74c8bb711f1a6abbc241121aa0a.nasl

Version: 1.1

Type: Local

Family: FreeBSD Local Security Checks

Published: 7/30/2026

Updated: 7/30/2026

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5

Vector: CVSS2#AV:L/AC:L/Au:N/C:P/I:C/A:C

CVSS Score Source: CVE-2026-58083

CVSS v3

Risk Factor: High

Base Score: 7.8

Temporal Score: 6.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:freebsd:freebsd, p-cpe:/a:freebsd:freebsd:freebsd-kernel

Required KB Items: Settings/ParanoidReport, Host/local_checks_enabled, Host/FreeBSD/release, Host/FreeBSD/pkg_info

Exploit Ease: No known exploits are available

Patch Publication Date: 7/30/2026

Vulnerability Publication Date: 7/30/2026

Reference Information

CVE: CVE-2026-58083

Detections

Analytics