CVE-2025-39759

System crash via unlocked qgroup teardown race

Published Sep 11, 2025 · Updated May 12, 2026

Use-after-free in btrfs qgroup code in Linux and SIMATIC CN 4100 before 5.0 allows local users to crash the affected system. btrfs_free_qgroup_config frees records from fs_info->qgroup_tree without qgroup_lock while qgroup_rescan_zero_tracking traverses that tree under the lock. Triggering the race requires local low-privileged access, enabled btrfs quotas, and concurrent quota-disable and rescan operations; the documented consequence on CN 4100 is loss of availability.

CVSS severity5.5
Medium
EPSS probability0.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Use-after-free in btrfs qgroup code in Linux and SIMATIC CN 4100 before 5.0 allows local users to crash the affected system. btrfs_free_qgroup_config frees records from fs_info->qgroup_tree without qgroup_lock while qgroup_rescan_zero_tracking traverses that tree under the lock. Triggering the race requires local low-privileged access, enabled btrfs quotas, and concurrent quota-disable and rescan operations; the documented consequence on CN 4100 is loss of availability.

The record

CVE
CVE-2025-39759
Published
Sep 11, 2025
Updated
May 12, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-20, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 11, 2025CVE publishedPublication date reported by the CVE source.
  2. May 12, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.12
  2. Affected versionversion=e685da14af6b31e4b336a110cb1bae1afc268be8 <2fd0f5ceb997f90f4332ccbab6c7e907e6b2d0eb
  3. Affected versionversion=e685da14af6b31e4b336a110cb1bae1afc268be8 <7cda0fdde5d9890976861421d207870500f9aace
  4. Affected versionversion=e685da14af6b31e4b336a110cb1bae1afc268be8 <b172535ccba12f0cf7d23b3b840989de47fc104d
  5. Affected versionversion=e685da14af6b31e4b336a110cb1bae1afc268be8 <c38028ce0d0045ca600b6a8345a0ff92bfb47b66
  6. Affected versionversion=e685da14af6b31e4b336a110cb1bae1afc268be8 <dd0b28d877b293b1d7f8727a7de08ae36b6b9ef0
  7. Affected versionversion=e685da14af6b31e4b336a110cb1bae1afc268be8 <e1249667750399a48cafcf5945761d39fa584edf

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3.12; version=e685da14af6b31e4b336a110cb1bae1afc268be8 <2fd0f5ceb997f90f4332ccbab6c7e907e6b2d0eb; version=e685da14af6b31e4b336a110cb1bae1afc268be8 <7cda0fdde5d9890976861421d207870500f9aace; version=e685da14af6b31e4b336a110cb1bae1afc268be8 <b172535ccba12f0cf7d23b3b840989de47fc104d; version=e685da14af6b31e4b336a110cb1bae1afc268be8 <c38028ce0d0045ca600b6a8345a0ff92bfb47b66; version=e685da14af6b31e4b336a110cb1bae1afc268be8 <dd0b28d877b293b1d7f8727a7de08ae36b6b9ef0; version=e685da14af6b31e4b336a110cb1bae1afc268be8 <e1249667750399a48cafcf5945761d39fa584edf
Siemens · SIMATIC CN 4100version=0 <V5.0

Published CVSS scores

7.0UbuntuCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
5.5Siemens ProductCERTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1499.004Application or System Exploitation

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo