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.

CVSS v3.1 Score

6.2

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS — Exploit Prediction

0.0002

Probability of exploitation

0.06%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-269 CWE-269

CWE-732 CWE-732

Affected Products

Vendor	Product	Versions
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All
freebsd	freebsd	All

References

Advisories & Patches

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

Frequently Asked Questions

What is CVE-2026-6386? +

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. It has a CVSS v3.1 base score of 6.2 (MEDIUM).

How severe is CVE-2026-6386? +

CVE-2026-6386 has a CVSS v3.1 score of 6.2 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0002, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-6386? +

CVE-2026-6386 affects products from freebsd, specifically: freebsd. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-6386? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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