CVE-2025-21691: cachestat: fix page cache statistics permission checking

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-02-10 · updated 2026-06-17

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).

Affected products

Linux kernel: from 6.5 before 6.6.75; from 6.7 before 6.12.12; 6.13 — fixed in 6.12.12, 6.6.75

How to fix

Upgrade to a fixed version: Linux kernel 6.12.12, 6.6.75. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2025-21691 or the next vulnerability affects your stack