Always-Incorrect Control Flow Implementation in FreeBSD - CVE-2026-6386
Published: April 22, 2026
Vulnerability identifier: #VU126825
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-6386
CWE-ID: CWE-670
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vendor: FreeBSD Foundation
Affected software:
FreeBSD
FreeBSD
Detailed vulnerability description
The vulnerability allows a local user to overwrite memory to which the application would otherwise not have access.
The vulnerability exists due to improper handling of large page mappings in pmap_pkru_update_range() when applying protection keys to an address range. A local user can cause the kernel to treat userspace memory as a page table page to overwrite memory to which the application would otherwise not have access.
The issue only affects amd64 systems and involves 1GB largepage mappings created using the shm_create_largepage(3) interface.
How to mitigate CVE-2026-6386
Install security update from vendor's website.