CyberSecBulletin
CVE-2026-64239NVD status: Analyzed

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-64239 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions c0e37017a452addec873865c94cf7a665663a9b2, a5fa42214de55e43d165144727ce9facb9fc6b08, 0ba6c05156d9ff9fc6ca22b7690e2eec9eca66f7 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.12% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to c0e37017a452addec873865c94cf7a665663a9b2 or a5fa42214de55e43d165144727ce9facb9fc6b08 or 0ba6c05156d9ff9fc6ca22b7690e2eec9eca66f7 or 2c33177023c92e76806c535ddbffaa3d3fc37777, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.6.143 or 6.12.93 or 6.18.35 or 7.0.12, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux9277d0367ba18ef4bb98bafb1209e715844cdf7e up to, but not including, c0e37017a452addec873865c94cf7a665663a9b2; 9277d0367ba18ef4bb98bafb1209e715844cdf7e up to, but not including, a5fa42214de55e43d165144727ce9facb9fc6b08; 9277d0367ba18ef4bb98bafb1209e715844cdf7e up to, but not including, 0ba6c05156d9ff9fc6ca22b7690e2eec9eca66f7; 9277d0367ba18ef4bb98bafb1209e715844cdf7e up to, but not including, 2c33177023c92e76806c535ddbffaa3d3fc37777; 9277d0367ba18ef4bb98bafb1209e715844cdf7e up to, but not including, 441f92f7d386b85bad16de49db95a307cba048a2; 6.2c0e37017a452addec873865c94cf7a665663a9b2, a5fa42214de55e43d165144727ce9facb9fc6b08, 0ba6c05156d9ff9fc6ca22b7690e2eec9eca66f7, 2c33177023c92e76806c535ddbffaa3d3fc37777, 441f92f7d386b85bad16de49db95a307cba048a2
LinuxLinux Kernel6.2 up to, but not including, 6.6.143; 6.7 up to, but not including, 6.12.93; 6.13 up to, but not including, 6.18.35; 6.19 up to, but not including, 7.0.12; 7.16.6.143, 6.12.93, 6.18.35, 7.0.12

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Official description

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. 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. # damo start --damos_action stat # cd /sys/kernel/mm/damon/admin/kdamonds/0/ # for i in {1..10}; do echo update_schemes_tried_regions > state; done # 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.

More Use After Free vulnerabilities (CWE-416)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Use After Free vulnerabilities

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