Raw vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:NCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
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, ranked at the 5th 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
CVEs Like This One
Affected Assets
Mitigating Controls
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 (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.
A.5.1 only requires the existence of an overarching policy and topic-specific policies (including on access control); it does not itself enforce, implement, or act on permissions and therefore cannot stop CWE-732 from being exploitable.
A.5.12 only defines and communicates a classification scheme (with owners accountable for applying it); it does not itself enforce, restrict or decide any permissions, so the CWE-732 permission flaw can still be present and exploitable.
A.5.15 directly mandates determining access requirements, defining/enforcing topic-specific access control policy, assigning rights/restrictions by entity/role, consistency with classification, need-to-know, privileged access restrictions, segregation, formal authorization, and dynamic rules — which stops most improper privilege management from being exploitable; bounded remainder is flawed implementation of those rules (e.g. incorrect mapping or enforcement bugs).
A.5.18 directly governs the provisioning, review, modification and timely revocation of access rights (including for role changes, termination and privilege levels), which stops most improper privilege spheres from being exploitable even if the assignment flaw exists; the bounded remainder is flaws in the underlying enforcement mechanism itself (e.g. AC-3/A.8.3)
Defining and communicating authorization levels for each role limits the assignment of excessive or unnecessary privileges.
Monitoring supplier policy changes and conducting audits can reveal incorrect permission assignments on resources managed by the supplier, prompting corrective action before they are exploited.
Hardening callouts derived
DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.
- No fine-grained STIG row for CWE-269, a class-level weakness. Rules are authored against its narrower children: CWE-250, CWE-266, CWE-267, CWE-268, CWE-270, CWE-274.
- No fine-grained STIG row for CWE-732, a class-level weakness. Rules are authored against its narrower children: CWE-276, CWE-277, CWE-281.