CVE-2025-21691: cachestat: fix page cache statistics permission checking
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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
debian/linuxto a version that resolves this vulnerability.Fixed in 5.10.223-1Fixed in 5.10.234-1Fixed in 6.1.129-1Fixed in 6.1.135-1Fixed in 6.12.27-1 - Upgrade
Upgrade
Linux kernelto a version that resolves this vulnerability.Patch cachestat: fix page cache statistics permission checking - Upgrade
Upgrade
Linux kernelto a version that resolves this vulnerability.Patch cf264e1329fb - Upgrade
Upgrade
Linux kernelto a version that resolves this vulnerability.Patch 134fca9063ad
Event History
Frequently Asked Questions
What is the severity of CVE-2025-21691?
CVE-2025-21691 has been classified with a medium severity level due to possible permission issues in the page cache statistics.
How do I fix CVE-2025-21691?
To fix CVE-2025-21691, update your Linux kernel to the latest stable version that includes the patch for this vulnerability.
What systems are affected by CVE-2025-21691?
CVE-2025-21691 affects the Linux kernel, specifically versions that include the 'cachestat()' system call.
What is the nature of the vulnerability identified in CVE-2025-21691?
CVE-2025-21691 involves improper permission checking in the 'cachestat()' system call, which could lead to unauthorized access to cache statistics.
When was CVE-2025-21691 reported?
CVE-2025-21691 was reported following the implementation of the 'cachestat()' system call in the Linux kernel.