CVE-2026-6386

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.

PUBLISHED Reserved 2026-04-15 | Published 2026-04-22 | Updated 2026-04-22 | Assigner freebsd

Problem types

CWE-269 Improper Privilege Management

CWE-732 Incorrect Permission Assignment for Critical Resource

Product status

Credits

Nicholas Carlini using Claude, Anthropic finder

References

security.freebsd.org/advisories/FreeBSD-SA-26:11.amd64.asc vendor-advisory

cve.org (CVE-2026-6386)

nvd.nist.gov (CVE-2026-6386)

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