CVE-2025-39866Public exploit

Local kernel code execution via writeback race

Published Sep 19, 2025 · Updated Sep 19, 2025

Use-after-free in Linux kernel writeback allows local users to execute kernel code via concurrent inode writes and cgroup switching. __mark_inode_dirty() releases inode->i_lock before wb_wakeup_delayed() finishes, allowing inode_switch_wbs_work_fn() to free the old bdi_writeback before it is dereferenced. An unprivileged local account with file-write access and delegated cgroup activity can trigger the race, causing kernel-memory disclosure, kernel code execution, or a panic.

CVSS severity7.8
High
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux kernel writeback allows local users to execute kernel code via concurrent inode writes and cgroup switching. __mark_inode_dirty() releases inode->i_lock before wb_wakeup_delayed() finishes, allowing inode_switch_wbs_work_fn() to free the old bdi_writeback before it is dereferenced. An unprivileged local account with file-write access and delegated cgroup activity can trigger the race, causing kernel-memory disclosure, kernel code execution, or a panic.

The record

CVE
CVE-2025-39866
Published
Sep 19, 2025
Updated
Sep 19, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 19, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 19, 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=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1edc2feb9c759a9883dfe81cb5ed231412d8b2e4
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b187c976111960e6e54a6b1fff724f6e3d39406c
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <bf89b1f87c72df79cf76203f71fbf8349cd5c9de
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c8c14adf80bd1a6e4a1d7ee9c2a816881c26d17a
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <d02d2c98d25793902f65803ab853b592c7a96b29
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e63052921f1b25a836feb1500b841bff7a4a0456

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1edc2feb9c759a9883dfe81cb5ed231412d8b2e4; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b187c976111960e6e54a6b1fff724f6e3d39406c; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <bf89b1f87c72df79cf76203f71fbf8349cd5c9de; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c8c14adf80bd1a6e4a1d7ee9c2a816881c26d17a; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <d02d2c98d25793902f65803ab853b592c7a96b29; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e63052921f1b25a836feb1500b841bff7a4a0456

Published CVSS scores

7.8Linux kernel CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

Public exploit references

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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