FreeBSD Kernel kqueue Use-After-Free Local Privilege Escalation Vulnerability

October 16th, 2026
ZDI-26-784 ZDI-CAN-31968

CVE ID

CVE-2026-58093

CVSS Score

8.8 AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Affected Vendors

FreeBSD

Affected Products

Kernel

Vulnerability Details

This vulnerability allows local attackers to escalate privileges on affected installations of FreeBSD Kernel. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability.

The specific flaw exists within the handling of filedesc objects. The issue results from the lack of validating the existence of an object prior to performing operations on the object. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the kernel.

Additional Details

FreeBSD has issued an update to correct this vulnerability. More details can be found at:
https://www.freebsd.org/security/advisories/FreeBSD-SA-26:62.tty.asc

Disclosure Timeline

  • 2026-08-20 - Vulnerability reported to vendor
  • 2026-10-16 - Coordinated public release of advisory
  • 2026-10-16 - Advisory Updated

Credit

tsune of GMO Cybersecurity by Ierae, Inc.

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