CVE-2026-6386: Missing large page handling in pmap_pkru_update_range()
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 shmcreatelargepage(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 pmappkruupdaterange() to treat userspace memory as a page table page, and thus overwrite memory to which the application would otherwise not have access.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-6386?
CVE-2026-6386 is considered a medium-severity vulnerability.
How do I fix CVE-2026-6386?
To fix CVE-2026-6386, update to the patched version of the FreeBSD kernel that addresses this issue.
What is the impact of CVE-2026-6386 on FreeBSD systems?
CVE-2026-6386 could potentially allow unauthorized access to protected memory areas due to improper large page handling.
Which versions of FreeBSD are affected by CVE-2026-6386?
CVE-2026-6386 affects specific versions of the FreeBSD kernel but should be checked against the provided security advisories for exact details.
Is there a workaround for CVE-2026-6386 until I can apply the fix?
There are no known workarounds for CVE-2026-6386; applying the security updates is recommended.