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Response snapshot Oct 27, 2026, 20:26 UTC

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VulnerabilityCVE-2026-64239

Linux kernel: mm/damon/sysfs-schemes: delete tried region in regions_rmdirs()

In the Linux kernel, the following vulnerability has been resolved: mm/damon/sysfs-schemes: delete tried region in regions_rmdirs() DAMON sysfs maintains the DAMOS tried region directory objects via a linked list.

At a glance

Exploited
Not known
Severity
7.8 High (CVSS 3.1)
Chance of exploitation
0.1% in the next 30 days
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-64239 (opens a new tab)

What happened

In the Linux kernel, the following vulnerability has been resolved:

mm/damon/sysfs-schemes: delete tried region in regions_rmdirs()

DAMON sysfs maintains the DAMOS tried region directory objects via a linked list. When the user requests refresh of the directories, DAMON sysfs removes all the region directories first, and then generate updated regions directory on the empty space. The removal function (damon_sysfs_scheme_regions_rm_dirs()) only puts the kobj objects. Deletion of the container region object from the linked list is done inside the kobj release callback function.

If somehow the callback invocation is delayed, the list will contain regions list that gonna be freed. If the updated region directories creation is started in this situation, the list can be corrupted and use-after-free can happen.

Continue reading

Because the kobj objects are managed by only DAMON sysfs, the issue cannot happen in normal situation. But, such delays can be made on kernels that built with CONFIG_DEBUG_KOBJECT_RELEASE. On the kernel, the issue can indeed be reproduced like below.

dmesg | grep underflow

[ 89.296152] refcount_t: underflow; use-after-free.

Fix the issue by removing the region object from the list when decrementing the reference count.

Also update damos_sysfs_populate_region_dir() to add the region object to the list only after the kobject_init_and_add() is success, so that fail of kobject_init_and_add() is not leaving the deallocated object on the list.

The issue was discovered [1] by Sashiko.

Scores and how they were measured

CVSS base severity

7.8

Version 3.1As of

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.1%

Scored Percentile 1.6%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    NVD CVE-2026-64239 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  4. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  5. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-64239, scored 2026-10-27. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 27). Linux kernel: mm/damon/sysfs-schemes: delete tried region in regions_rmdirs() (CVE-2026-64239). https://kevwire.com/record/CVE-2026-64239

MLA

"Linux kernel: mm/damon/sysfs-schemes: delete tried region in regions_rmdirs() (CVE-2026-64239)." KEVWire, 27 Oct. 2026, kevwire.com/record/CVE-2026-64239.

Chicago

KEVWire. "Linux kernel: mm/damon/sysfs-schemes: delete tried region in regions_rmdirs() (CVE-2026-64239)." Last modified October 27, 2026. https://kevwire.com/record/CVE-2026-64239.

Evidence summary (plain text)

Linux kernel: mm/damon/sysfs-schemes: delete tried region in regions_rmdirs() (Jul 24, 2026).
In the Linux kernel, the following vulnerability has been resolved:

mm/damon/sysfs-schemes: delete tried region in regions_rmdirs()

DAMON sysfs maintains the DAMOS tried region directory objects via a
linked list.  When the user requests refresh of the directories, DAMON
sysfs removes all the region directories first, and then generate updated
regions directory on the empty space.  The removal function
(damon_sysfs_scheme_regions_rm_dirs()) only puts the kobj objects.
Deletion of the container region object from the linked list is done
inside the kobj release callback function.
CVSS 7.8 (version 3.1; evidence as of Oct 27, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-64239).
EPSS 0.1% for the following 30 days, scored Oct 27, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-64239&date=2026-10-27).
Sources:
NVD CVE-2026-64239: https://nvd.nist.gov/vuln/detail/CVE-2026-64239
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-27T18:01:06.567Z&lastModEndDate=2026-10-27T19:30:57.564Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-27T17:31:06.169Z&lastModEndDate=2026-10-27T19:00:56.846Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-27T17:00:59.751Z&lastModEndDate=2026-10-27T18:30:58.316Z&resultsPerPage=500&startIndex=0
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-64239&date=2026-10-27
Record ID: CVE-2026-64239.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 19:51 UTC. Ingestion is not an independent editorial investigation.

NVD status: Analyzed. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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