CVE-2025-21691

Local cache-state disclosure via missing ownership checks

Published Feb 10, 2025 · Updated May 11, 2026

Incorrect authorization in Linux kernel cachestat allows local users to obtain page-cache statistics for files they cannot write or own. The syscall reports cached-page counts for a supplied file descriptor without checking that the caller can write the file or owns its inode. A local low-privilege process needs a valid file descriptor; the result exposes access patterns and cached-data presence, not file contents directly.

CVSS severity5.5
Medium
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in Linux kernel cachestat allows local users to obtain page-cache statistics for files they cannot write or own. The syscall reports cached-page counts for a supplied file descriptor without checking that the caller can write the file or owns its inode. A local low-privilege process needs a valid file descriptor; the result exposes access patterns and cached-data presence, not file contents directly.

The record

CVE
CVE-2025-21691
Published
Feb 10, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-863
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 10, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.5
  2. Affected versionversion=cf264e1329fb0307e044f7675849f9f38b44c11a <5f537664e705b0bf8b7e329861f20128534f6a83
  3. Affected versionversion=cf264e1329fb0307e044f7675849f9f38b44c11a <780ab8329672464984cf1344bd5c3993af0226c7
  4. Affected versionversion=cf264e1329fb0307e044f7675849f9f38b44c11a <7d6405c13b0d8a8367cd8df63f118b619a3f0dd2
  5. Affected versionversion=cf264e1329fb0307e044f7675849f9f38b44c11a <97153a05077f618f7471f50a78158602badccb30

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.5; version=cf264e1329fb0307e044f7675849f9f38b44c11a <5f537664e705b0bf8b7e329861f20128534f6a83; version=cf264e1329fb0307e044f7675849f9f38b44c11a <780ab8329672464984cf1344bd5c3993af0226c7; version=cf264e1329fb0307e044f7675849f9f38b44c11a <7d6405c13b0d8a8367cd8df63f118b619a3f0dd2; version=cf264e1329fb0307e044f7675849f9f38b44c11a <97153a05077f618f7471f50a78158602badccb30

Published CVSS scores

7.1Oracle LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
5.5UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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