CVE-2026-58086
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Privilege Escalation in FreeBSD Jail via ktrace Misconfiguration

Publication date: 2026-08-19

Last updated on: 2026-08-31

Assigner: FreeBSD

Description
As an inadvertent side effect of an unrelated code change, PRIV_KTRACE was always denied to a jailed root user. Tracing configured by a jailed root user was therefore not flagged as privileged. An unprivileged user in a jail that has permission to debug the target process can modify the jailed root user's ktrace(2) flags, or disable tracing outright. A jailed root user therefore cannot reliably trace unprivileged processes.

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Meta Information

Published
2026-08-19
Last Modified
2026-08-31
Generated
2026-09-08
AI Q&A
2026-08-19
EPSS Evaluated
2026-09-07
NVD
CVE-2026-58086
EUVD
EUVD-2026-62340

Affected Vendors & Products

Showing 16 associated CPEs
Vendor Product Version / Range
freebsd freebsd 15.0
freebsd freebsd 15.0
freebsd freebsd 15.0
freebsd freebsd 15.0
freebsd freebsd 15.0
freebsd freebsd 15.0
freebsd freebsd 15.0
freebsd freebsd 15.0
freebsd freebsd 15.0
freebsd freebsd 15.0
freebsd freebsd 15.1
freebsd freebsd 15.0
freebsd freebsd 15.0
freebsd freebsd 15.1
freebsd freebsd 15.1
freebsd freebsd 15.1

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-273 The product attempts to drop privileges but does not check or incorrectly checks to see if the drop succeeded.

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Executive Summary

This vulnerability in FreeBSD versions 15.1 and 15.0 involves incorrect privilege validation in jails. Due to an unrelated code change, the PRIV_KTRACE privilege is always denied to a jailed root user. This allows unprivileged users within the jail to modify or disable ktrace(2) tracing flags set by the jailed root user, preventing reliable tracing of unprivileged processes.

Detection Guidance

Detecting this vulnerability requires checking the FreeBSD version and whether ktrace(2) is affected. Run 'freebsd-version' to verify your FreeBSD version. If running 15.1 or 15.0, the system may be vulnerable. Check ktrace(2) behavior by attempting to trace a process as a jailed root user to see if tracing is unreliable or can be disabled.

Impact Analysis

If you are a jailed root user on FreeBSD 15.1 or 15.0, an unprivileged user in the same jail could interfere with your ktrace(2) tracing, potentially hiding malicious activity or disrupting debugging. This compromises system monitoring and security oversight within the jail environment.

Compliance Impact

The vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards as it relates to FreeBSD's ktrace(2) facility and privilege validation in jails. However, if tracing is used for auditing or monitoring purposes, the inability to reliably trace processes could impact compliance reporting or forensic investigations.

Mitigation Strategies

Upgrade to a supported FreeBSD stable or release/security branch dated after July 29, 2026. Use pkg(8), freebsd-update(8), or apply a source code patch. After updating, reboot the system to ensure changes take effect.

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