# 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…

Source: https://junglewise.ai/threats/cve-2026-58083-while-the-kernel-was-copying-knotes-during-fork-a-knote-with-a  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-19  
License: CC BY 4.0 with a link back

CVE-2026-58083 · Severity: high · CVSS 8.4 · Published 2026-08-19

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.

Technologies: [Freebsd](https://junglewise.ai/threats/technologies/freebsd). Vendors: [Freebsd](https://junglewise.ai/threats/vendors/freebsd).

## Quick answers

**Is CVE-2026-58083 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-58083 being exploited in the wild.

**How severe is CVE-2026-58083?** High severity, with a CVSS score of 8.4, published 19 August 2026.

**Which products and versions are affected?** Freebsd. The advisory does not name versions.

**Is there a fix for CVE-2026-58083?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**Am I affected by CVE-2026-58083?** Check whether you run Freebsd. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Freebsd

## Related threats

- [FreeBSD kqueue out-of-bounds read in fork copy](https://junglewise.ai/threats/cve-2026-58100-kqueue-fork-copy-knote-indexed-into-the-child-s-file-descriptor)
- [FreeBSD kernel kqueue memory safety bugs in copy-on-fork](https://junglewise.ai/threats/cve-2026-58099-when-copying-knotes-from-a-parent-kqueue-to-a-child-the-copy-code)
- [FreeBSD kernel heap out-of-bounds access in semop(2)](https://junglewise.ai/threats/cve-2026-58098-when-semop-2-blocks-waiting-for-a-semaphore-condition-it-releases)
- [FreeBSD sound(4) use-after-free in buffer resize TOCTOU race](https://junglewise.ai/threats/cve-2026-101308-when-an-audio-channel-s-buffer-needs-to-be-resized-the-sound-4)
- [FreeBSD RACK stack buffer overflow in tcp_rack](https://junglewise.ai/threats/cve-2026-101307-when-the-pcm-sample-array-needs-to-grow-the-rack-stack-doubles-a)