CyberSecBulletin
CVE-2025-39759NVD status: Modified

Linux: Concurrent Execution using Shared Resource with Improper Synchronization

Published Updated By the CyberSecBulletin desk

CVE-2025-39759 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Linux, with a CVSS 3.1 base score of 7.0 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 7cda0fdde5d9890976861421d207870500f9aace, b172535ccba12f0cf7d23b3b840989de47fc104d, dd0b28d877b293b1d7f8727a7de08ae36b6b9ef0 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 7cda0fdde5d9890976861421d207870500f9aace or b172535ccba12f0cf7d23b3b840989de47fc104d or dd0b28d877b293b1d7f8727a7de08ae36b6b9ef0 or c38028ce0d0045ca600b6a8345a0ff92bfb47b66, whichever matches your release line, or a later version.
  2. Update SIMATIC CN 4100 to V5.0 or a later version.
  3. Update Linux Kernel to 6.1.149 or 6.6.103 or 6.12.44 or 6.15.11, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxe685da14af6b31e4b336a110cb1bae1afc268be8 up to, but not including, 7cda0fdde5d9890976861421d207870500f9aace; e685da14af6b31e4b336a110cb1bae1afc268be8 up to, but not including, b172535ccba12f0cf7d23b3b840989de47fc104d; e685da14af6b31e4b336a110cb1bae1afc268be8 up to, but not including, dd0b28d877b293b1d7f8727a7de08ae36b6b9ef0; e685da14af6b31e4b336a110cb1bae1afc268be8 up to, but not including, c38028ce0d0045ca600b6a8345a0ff92bfb47b66; e685da14af6b31e4b336a110cb1bae1afc268be8 up to, but not including, 2fd0f5ceb997f90f4332ccbab6c7e907e6b2d0eb; e685da14af6b31e4b336a110cb1bae1afc268be8 up to, but not including, e1249667750399a48cafcf5945761d39fa584edf; 3.127cda0fdde5d9890976861421d207870500f9aace, b172535ccba12f0cf7d23b3b840989de47fc104d, dd0b28d877b293b1d7f8727a7de08ae36b6b9ef0, c38028ce0d0045ca600b6a8345a0ff92bfb47b66, 2fd0f5ceb997f90f4332ccbab6c7e907e6b2d0eb, e1249667750399a48cafcf5945761d39fa584edf
SiemensSIMATIC CN 4100before V5.0V5.0
LinuxLinux Kernel3.12 up to, but not including, 6.1.149; 6.2 up to, but not including, 6.6.103; 6.7 up to, but not including, 6.12.44; 6.13 up to, but not including, 6.15.11; 6.16 up to, but not including, 6.16.26.1.149, 6.6.103, 6.12.44, 6.15.11, 6.16.2
DebianDebian Linux11.0Not stated

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
HighSuccess depends on conditions outside the attacker's control.
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:H/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: btrfs: qgroup: fix race between quota disable and quota rescan ioctl There's a race between a task disabling quotas and another running the rescan ioctl that can result in a use-after-free of qgroup records from the fs_info->qgroup_tree rbtree. This happens as follows: 1) Task A enters btrfs_ioctl_quota_rescan() -> btrfs_qgroup_rescan(); 2) Task B enters btrfs_quota_disable() and calls btrfs_qgroup_wait_for_completion(), which does nothing because at that point fs_info->qgroup_rescan_running is false (it wasn't set yet by task A); 3) Task B calls btrfs_free_qgroup_config() which starts freeing qgroups from fs_info->qgroup_tree without taking the lock fs_info->qgroup_lock; 4) Task A enters qgroup_rescan_zero_tracking() which starts iterating the fs_info->qgroup_tree tree while holding fs_info->qgroup_lock, but task B is freeing qgroup records from that tree without holding the lock, resulting in a use-after-free. Fix this by taking fs_info->qgroup_lock at btrfs_free_qgroup_config(). Also at btrfs_qgroup_rescan() don't start the rescan worker if quotas were already disabled.

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

The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

How developers prevent this class of flaw

  • In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
  • Use thread-safe capabilities such as the data access abstraction in Spring.
  • Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

More Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities (CWE-362)

Timeline

  1. CVE record published.
  2. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities

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