CVE-2025-21691: cachestat: fix page cache statistics permission checking
Vulnerability summary
CVE-2025-21691 is a medium (CVSS 5.5) vulnerability in linux. EPSS estimates a 0.20% chance of exploitation in the next 30 days, higher than 10.4% of scored vulnerabilities.
Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 15 · Related 10Timeline
- 10-02-2025PublishedVulnerability first disclosed.
- 11-05-2026Last modifiedVulnerability information updated.
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).
CVSS metrics
3 scores · 3 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.20%
Chance of exploitation in the next 30 days
Percentile
10%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.20% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeNo weakness data has been published for this record.
Affected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu106 products
- linux< 6.8.0-62.65
- linux-allwinner-5.19All versions (No fix recorded)
- linux-aws< 6.8.0-1030.32
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ cf264e1329fb0307e044f7675849f9f38b44c11a, < 7d6405c13b0d8a8367cd8df63f118b619a3f0dd2 | ≥ cf264e1329fb0307e044f7675849f9f38b44c11a, < 780ab8329672464984cf1344bd5c3993af0226c7 | ≥ cf264e1329fb0307e044f7675849f9f38b44c11a, < 97153a05077f618f7471f50a78158602badccb30 | ≥ cf264e1329fb0307e044f7675849f9f38b44c11a, < 5f537664e705b0bf8b7e329861f20128534f6a83 | 6.5
- linux_kernelEOL≥ 6.5, < 6.6.75 | ≥ 6.7, < 6.12.12 | 6.13
Debian1 product
- linux< 6.12.12-1
3 vendors · 109 products
