CVE-2026-89639

Stale file-data disclosure via missing cache invalidation

Published Sep 11, 2026 · Updated Sep 11, 2026

Improper cache invalidation in the Linux kernel CIFS client allows attackers to read stale file data after an O_TRUNC open. cifs_do_truncate() calls cifs_setsize() without invalidating the fscache cookie, so later cookie activation can serve data that truncation made invalid. Exposure requires a CIFS file to be opened with O_TRUNC while filesystem caching is involved, and the bounded consequence is disclosure of stale file contents.

CVSS severityUnavailable
Unscored
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper cache invalidation in the Linux kernel CIFS client allows attackers to read stale file data after an O_TRUNC open. cifs_do_truncate() calls cifs_setsize() without invalidating the fscache cookie, so later cookie activation can serve data that truncation made invalid. Exposure requires a CIFS file to be opened with O_TRUNC while filesystem caching is involved, and the bounded consequence is disclosure of stale file contents.

The record

CVE
CVE-2026-89639
Published
Sep 11, 2026
Updated
Sep 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1005
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 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=3513f3931c579ba2a715784c6dedc59e0d9282ee
  2. Affected versionversion=6.12.105 <6.13
  3. Affected versionversion=6.18.44 <6.18.50
  4. Affected versionversion=6838bcac954487cc0a3c8a4ee1b3a3a30e244dc9
  5. Affected versionversion=7.1.8 <7.2
  6. Affected versionversion=7.2
  7. Affected versionversion=75640976cf474eb41682a13f2dbe9534ac26ca50
  8. Affected versionversion=efbcecdecefc26fa062c0e8210533ccad7d6bd4a <8b9b10fe5b8b492b27b9f4546742ea541a650213
  9. Affected versionversion=fa724e235cfdb0fb0bb427d0f9dfe864ae27403e <364b183230586a62660a7280c1eb20138338eeb5
  10. Affected versionversion=fa724e235cfdb0fb0bb427d0f9dfe864ae27403e <81fc3868a7f726980ff845c1d0d271051e5f0f45

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=3513f3931c579ba2a715784c6dedc59e0d9282ee; version=6.12.105 <6.13; version=6.18.44 <6.18.50; version=6838bcac954487cc0a3c8a4ee1b3a3a30e244dc9; version=7.1.8 <7.2; version=7.2; version=75640976cf474eb41682a13f2dbe9534ac26ca50; version=efbcecdecefc26fa062c0e8210533ccad7d6bd4a <8b9b10fe5b8b492b27b9f4546742ea541a650213; version=fa724e235cfdb0fb0bb427d0f9dfe864ae27403e <364b183230586a62660a7280c1eb20138338eeb5; version=fa724e235cfdb0fb0bb427d0f9dfe864ae27403e <81fc3868a7f726980ff845c1d0d271051e5f0f45

Published CVSS scores

No CVSS assessment is available in this record.

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)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1005Data from Local System

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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