CVE-2025-40021

Tracefs lockdown bypass via unchecked dynamic_events open

Published Oct 24, 2025 · Updated Oct 24, 2025

Improper access control in affected Linux kernel branches beginning with 5.4 allows local privileged users to bypass tracefs lockdown. The dyn_event_open function opens tracefs dynamic_events without calling security_locked_down for LOCKDOWN_TRACEFS. Exploitation requires local privileged tracefs access and enabled kernel lockdown, after which probe events can be added despite that restriction.

CVSS severityUnavailable
Unscored
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in affected Linux kernel branches beginning with 5.4 allows local privileged users to bypass tracefs lockdown. The dyn_event_open function opens tracefs dynamic_events without calling security_locked_down for LOCKDOWN_TRACEFS. Exploitation requires local privileged tracefs access and enabled kernel lockdown, after which probe events can be added despite that restriction.

The record

CVE
CVE-2025-40021
Published
Oct 24, 2025
Updated
Oct 24, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1562.001
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Oct 24, 2025CVE publishedPublication date reported by the CVE source.
  2. Oct 24, 2025Record 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=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <07b1f63b5f86765793fab44d3d4c2be681cddafb
  2. Affected versionversion=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <0d41604d2d53c1abe27fefb54b37a8f6642a4d74
  3. Affected versionversion=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <3887f3814c0e770e6b73567fe0f83a2c01a6470c
  4. Affected versionversion=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <456c32e3c4316654f95f9d49c12cbecfb77d5660
  5. Affected versionversion=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <573b1e39edfcb7b4eecde0f1664455a1f4462eee
  6. Affected versionversion=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <b47c4e06687a5a7b6c6ef4bd303fcfe4430b26bb
  7. Affected versionversion=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <f3ac1f4eaba58e57943efa3e8b8d71fa7aab0abf
  8. Affected versionversion=5.4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linuxversion=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <07b1f63b5f86765793fab44d3d4c2be681cddafb; version=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <0d41604d2d53c1abe27fefb54b37a8f6642a4d74; version=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <3887f3814c0e770e6b73567fe0f83a2c01a6470c; version=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <456c32e3c4316654f95f9d49c12cbecfb77d5660; version=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <573b1e39edfcb7b4eecde0f1664455a1f4462eee; version=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <b47c4e06687a5a7b6c6ef4bd303fcfe4430b26bb; version=17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 <f3ac1f4eaba58e57943efa3e8b8d71fa7aab0abf; version=5.4

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

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1562.001Impair Defenses: Disable or Modify Tools

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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