CVE-2026-6386

CVE-2026-6386 is a medium-severity vulnerability in Freebsd with a CVSS 3.x base score of 6.2. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-269.

Key facts

Description

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 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.

Frequently asked questions

What is CVE-2026-6386?
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 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.
How severe is CVE-2026-6386?
CVE-2026-6386 has a CVSS 3.x base score of 6.2, rated medium severity. It is exploitable over local access with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-6386 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (6th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-6386?
CVE-2026-6386 primarily affects Freebsd. In total, 33 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-6386?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-6386 have an EU (EUVD) identifier?
Yes. CVE-2026-6386 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24592.
When was CVE-2026-6386 published?
CVE-2026-6386 was published on 2026-04-22 and last updated on 2026-06-17.

References

Affected products (33)

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