CVE-2026-58084
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Kernel Stack Memory Leak in FreeBSD POSIX Timer

Publication date: 2026-08-19

Last updated on: 2026-08-31

Assigner: FreeBSD

Description
To retrieve the previous timer value, the kernel calls realtimer_gettime(), which obtains the current time for the timer's clock. For a timer using CLOCK_TAI this can fail when no TAI offset has been configured, but the error return was not checked, so the uninitialized output buffer was copied to userspace. An unprivileged local user can obtain uninitialized kernel stack memory by creating a POSIX timer with CLOCK_TAI and calling timer_settime(2), potentially disclosing sensitive kernel data.

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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-2026-58084
EUVD
EUVD-2026-62338

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-908 The product uses or accesses a resource that has not been initialized.

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Executive Summary

CVE-2026-58084 is a FreeBSD kernel vulnerability where an unprivileged local user can access uninitialized kernel stack memory. It occurs when using timer_settime(2) with a POSIX timer set to CLOCK_TAI. The kernel fails to check an error in realtimer_gettime(), copying uninitialized memory to userspace, potentially exposing sensitive kernel data.

Detection Guidance

This vulnerability can be detected by checking the FreeBSD version and verifying if the system is running a vulnerable release. Use 'freebsd-version' or 'uname -r' to check the version. If the system is running FreeBSD 15.1 or 15.0 without the latest patches, it may be vulnerable.

Impact Analysis

An attacker could exploit this to read uninitialized kernel memory, which may contain sensitive information like passwords, encryption keys, or other confidential data. This could lead to privilege escalation or further system compromise if combined with other vulnerabilities.

Compliance Impact

This vulnerability could lead to unauthorized disclosure of personal or sensitive data, violating GDPR and HIPAA requirements for data protection. Organizations may face compliance penalties if exploited, as it undermines confidentiality controls.

Mitigation Strategies

Immediately upgrade the system using 'pkg upgrade', 'freebsd-update', or apply a source code patch. After updating, reboot the system to ensure the changes take effect. No workaround is available, so upgrading is the only mitigation.

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