CVE-2026-6386 Missing large page handling in pmap_pkru_update_range()
An unprivileged user can exploit missing large page handling in the FreeBSD kernel to overwrite protected memory, potentially leading to privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-6386?
CVE-2026-6386 is a medium-severity vulnerability in Freebsd Freebsd, published on 22 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-6386?
It affects 1 product.
Products include Freebsd Freebsd.
How do I fix CVE-2026-6386?
No fix has been published for CVE-2026-6386 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-6386 being exploited?
There is no known exploitation of CVE-2026-6386 in the wild and no public exploit code.
Other vulnerabilities in Freebsd Freebsd
Sources
Also known as GHSA-99g5-mwj2-6xjq.