CVE-2025-21691: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: cachestat: fix page cache statistics permission checking When the 'cachestat()' system call was added in commit cf264e1329fb ("cachestat: implement cachestat syscall"), it was meant to be a much more convenient (and performant) version of mincore() that didn't need mapping things into the user virtual address space in order to work. But it ended up missing the "check for writability or ownership" fix for mincore(), done in commit 134fca9063ad ("mm/mincore.c: make mincore() more conservative"). This just adds equivalent logic to 'cachestat()', modified for the file context (rather than vma).

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CVSS v3.1 Score

5.5

MEDIUM

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

Affected Products

Vendor	Product	Versions
linux	linux_kernel	6.5 — 6.6.75
linux	linux_kernel	6.7 — 6.12.12
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/5f537664e705b0bf8b7e329861f20128534f6a83 https://git.kernel.org/stable/c/780ab8329672464984cf1344bd5c3993af0226c7 https://git.kernel.org/stable/c/7d6405c13b0d8a8367cd8df63f118b619a3f0dd2 https://git.kernel.org/stable/c/97153a05077f618f7471f50a78158602badccb30

Frequently Asked Questions

What is CVE-2025-21691? +

In the Linux kernel, the following vulnerability has been resolved: cachestat: fix page cache statistics permission checking When the 'cachestat()' system call was added in commit cf264e1329fb ("cachestat: implement cachestat syscall"), it was meant to be a much more convenient (and performant) version of mincore() that didn't need mapping things into the user virtual address space in order to work. But it ended up missing the "check for writability or ownership" fix for mincore(), done in commit 134fca9063ad ("mm/mincore.c: make mincore() more conservative"). This just adds equivalent logic to 'cachestat()', modified for the file context (rather than vma). It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-21691? +

CVE-2025-21691 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-21691? +

CVE-2025-21691 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-21691? +

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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CVE-2025-21691