CVE-2026-58089
Received Received - Intake

PMC Monitoring Bypass in FreeBSD Kernel

Publication date: 2026-08-26

Last updated on: 2026-08-26

Assigner: FreeBSD

Description
When a process calls execve(2) to execute a setuid or setgid image, hwpmc(4) is supposed to detach PMCs owned by unprivileged processes. An inverted check meant that this scenario was not handled properly. An unprivileged local user who has attached PMCs to a process can continue monitoring it after the process executes a setuid or setgid binary, contrary to the intended policy.

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Meta Information

Published
2026-08-26
Last Modified
2026-08-26
Generated
2026-08-26
AI Q&A
2026-08-26
EPSS Evaluated
N/A
NVD
CVE-2026-58089
EUVD
EUVD-2026-66234

Affected Vendors & Products

Currently, no data is known.

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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 involves a flaw in the hwpmc(4) component of FreeBSD. When a process executes a setuid or setgid binary using execve(2), the system is supposed to detach Performance Monitoring Counters (PMCs) owned by unprivileged processes. However, an inverted check prevents this detachment, allowing unprivileged local users to continue monitoring processes even after they execute privileged binaries.

Impact Analysis

An attacker with local access could exploit this to monitor sensitive processes after privilege escalation, potentially leaking confidential information or enabling further attacks by observing program behavior or data access patterns.

Mitigation Strategies

Apply the vendor-supplied patch or update for FreeBSD systems to fix the inverted check in hwpmc(4). Disable PMC monitoring for unprivileged processes until patched.

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