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 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: 2026-04-22 Last update: 2026-05-01 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-6386 is rated Low Risk (27/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.16%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-6386

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.02% 0.16% +0.14%
2 2026-04-22 — 0.02% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-6386

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.2 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 2.5 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-6386

GitHub Security Advisory for CVE-2026-6386

GHSA-99g5-mwj2-6xjq · Severity: medium — In order to apply a particular protection key to an address range, the kernel must update the...

Affected software / configurations for CVE-2026-6386

Vendor Product Version Raw CPE
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:-:*:*:*:*:*:*
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:beta3:*:*:*:*:*:*
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:p1:*:*:*:*:*:*
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:p10:*:*:*:*:*:*
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:p11:*:*:*:*:*:*
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:p2:*:*:*:*:*:*
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:p3:*:*:*:*:*:*
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:p4:*:*:*:*:*:*
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:p5:*:*:*:*:*:*
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:p6:*:*:*:*:*:*
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:p7:*:*:*:*:*:*
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:p8:*:*:*:*:*:*
freebsd freebsd 13.5 cpe:2.3:o:freebsd:freebsd:13.5:p9:*:*:*:*:*:*
freebsd freebsd 14.3 cpe:2.3:o:freebsd:freebsd:14.3:-:*:*:*:*:*:*
freebsd freebsd 14.3 cpe:2.3:o:freebsd:freebsd:14.3:p1:*:*:*:*:*:*
freebsd freebsd 14.3 cpe:2.3:o:freebsd:freebsd:14.3:p10:*:*:*:*:*:*
freebsd freebsd 14.3 cpe:2.3:o:freebsd:freebsd:14.3:p2:*:*:*:*:*:*
freebsd freebsd 14.3 cpe:2.3:o:freebsd:freebsd:14.3:p3:*:*:*:*:*:*
freebsd freebsd 14.3 cpe:2.3:o:freebsd:freebsd:14.3:p4:*:*:*:*:*:*
freebsd freebsd 14.3 cpe:2.3:o:freebsd:freebsd:14.3:p5:*:*:*:*:*:*
freebsd freebsd 14.3 cpe:2.3:o:freebsd:freebsd:14.3:p6:*:*:*:*:*:*
freebsd freebsd 14.3 cpe:2.3:o:freebsd:freebsd:14.3:p7:*:*:*:*:*:*
freebsd freebsd 14.3 cpe:2.3:o:freebsd:freebsd:14.3:p8:*:*:*:*:*:*
freebsd freebsd 14.3 cpe:2.3:o:freebsd:freebsd:14.3:p9:*:*:*:*:*:*
freebsd freebsd 14.4 cpe:2.3:o:freebsd:freebsd:14.4:-:*:*:*:*:*:*
freebsd freebsd 14.4 cpe:2.3:o:freebsd:freebsd:14.4:p1:*:*:*:*:*:*
freebsd freebsd 14.4 cpe:2.3:o:freebsd:freebsd:14.4:rc1:*:*:*:*:*:*
freebsd freebsd 15.0 cpe:2.3:o:freebsd:freebsd:15.0:-:*:*:*:*:*:*
freebsd freebsd 15.0 cpe:2.3:o:freebsd:freebsd:15.0:p1:*:*:*:*:*:*
freebsd freebsd 15.0 cpe:2.3:o:freebsd:freebsd:15.0:p2:*:*:*:*:*:*
freebsd freebsd 15.0 cpe:2.3:o:freebsd:freebsd:15.0:p3:*:*:*:*:*:*
freebsd freebsd 15.0 cpe:2.3:o:freebsd:freebsd:15.0:p4:*:*:*:*:*:*
freebsd freebsd 15.0 cpe:2.3:o:freebsd:freebsd:15.0:p5:*:*:*:*:*:*

References for CVE-2026-6386

cvelogic Threat Intelligence