Raw vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:NSummary
CVE-2026-6386 is a medium-severity Improper Privilege Management (CWE-269) vulnerability in Freebsd Freebsd. Its CVSS base score is 6.2 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Abuse Elevation Control Mechanism (T1548); ranked at the 6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-2 (Account Management) and AC-24 (Access Control Decisions) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-6386 is a vulnerability in the FreeBSD kernel's pmap_pkru_update_range() subroutine on the amd64 architecture. The issue arises when applying a protection key to an address range, as the subroutine fails to account for 1GB largepage mappings created via the shm_create_largepage(3) interface. It incorrectly assumes that page directory page entries always point to another page table page, leading to improper handling of page table updates.
An unprivileged local user can exploit this flaw to cause pmap_pkru_update_range() to treat userspace memory as a page table page. This enables the attacker to overwrite memory regions that the application would otherwise lack access to, resulting in unauthorized memory modification. The vulnerability is scored at CVSS 6.2 (CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N) and is associated with CWE-269 (Improper Privilege Management) and CWE-732 (Incorrect Permission Assignment for Critical Resource).
Mitigation details and patches are documented in the FreeBSD Security Advisory FreeBSD-SA-26:11.amd64, available at https://security.freebsd.org/advisories/FreeBSD-SA-26:11.amd64.asc.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-24592
Vulnerability Data
In order to apply a particular protection key to an address range, the kernel must update the corresponding page table entries. The subroutine which handled this failed to take into account the presence of 1GB largepage mappings created using the…
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shm_create_largepage(3) interface. In particular, it would always treat a page directory page entry as pointing to another page table page. The bug can be abused by an unprivileged user to cause pmap_pkru_update_range() to treat userspace memory as a page table page, and thus overwrite memory to which the application would otherwise not have access.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 12 hardening rules · 6 OS baselines
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Mitigating Controls (NIST 800-53 r5) AI
Enforces the access control policy that defines permissions on resources, thereby stopping incorrect assignments from remaining exploitable.
Account management directly governs assignment and tracking of privileges so proper implementation stops the weakness from being introduced.
Requiring explicit access-control decisions ensures privileges are evaluated rather than assumed or omitted.
Separation of duties constrains how privileges may be assigned, reducing the chance of overly broad actor control.
Least privilege is the direct countermeasure to improper privilege management; implementing it eliminates the root cause.
Binding security attributes to subjects/objects supplies the mechanism needed to track and enforce privileges correctly.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Directly requires defining, enforcing, and reviewing access permissions and least privilege on resources.
Hardened baselines and configuration management explicitly include correct permission settings for critical resources.
PR.AA-01 supplies credential/identity lifecycle support that can reduce some privilege-assignment errors but does not itself assign, modify, or check privileges, leaving most of CWE-269's risk unaddressed.
PR.PS-05 can partially limit exploitability of some privilege issues via execution restrictions, but does not address the core design/implementation flaws of CWE-269 at all.
PR.DS-10 protects data-in-use without touching privilege assignment/tracking, so it neither prevents CWE-269 nor removes more than one narrow facet of its risk.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
By requiring owners to determine and document the exact permissions needed for each asset, the control reduces the likelihood that default or overly permissive file and resource permissions will be left in place.
Requiring owner approval, segregation of duties, and periodic reviews prevents the assignment of excessive or unnecessary privileges to users or processes.
Enforcing minimum-necessary privileges, temporary grants, and separation of administrative versus normal identities prevents the over-assignment of rights that CWE-269 describes.
Dynamic techniques that grant the minimum necessary rights for a given time window and revoke them afterward reduce the window in which excessive or unnecessary privileges can be exploited.
Enforcing differentiated permissions on the source-code repository and program listings stops the assignment of overly broad default or inherited permissions to critical resources.
By defining and enforcing secure permission settings in configuration templates, the control reduces the likelihood that critical resources receive incorrect permission assignments.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (1 rule)
- V-248577 OL 8 must enable kernel parameters to enforce Discretionary Access Control (DAC) on symlinks. prevents CWE-732
Windows 10 (1 rule)
- V-220712 Only accounts responsible for the administration of a system must have Administrator rights on the system. prevents CWE-269
Windows 11 (1 rule)
- V-253269 prevents CWE-269
Windows Server 2016 (3 rules)
- V-224972 Active Directory Group Policy objects must have proper access control permissions. prevents CWE-732
- V-225007 Only administrators responsible for the member server or standalone or nondomain-joined system must have Administrator rights on the system. prevents CWE-269
- V-224831 Local volumes must use a format that supports NTFS attributes. prevents CWE-732
Windows Server 2019 (3 rules)
- V-205741 Windows Server 2019 Active Directory Group Policy objects must have proper access control permissions. prevents CWE-732
- V-205746 Windows Server 2019 must only allow Administrators responsible for the member server or standalone or nondomain-joined system to have Administrator rights on the system. prevents CWE-269
- V-205663 Windows Server 2019 local volumes must use a format that supports NTFS attributes. prevents CWE-732
Windows Server 2022 (3 rules)
- V-254393 prevents CWE-732
- V-254428 prevents CWE-269
- V-254250 prevents CWE-732