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Linux KernelOperating system · Linux

CVE-2025-39759

HIGH · 7.0 CVSS v3.1 Published 2025-09-11
Fix available
A fix is available. Upgrade to 6.1.149 / 6.6.103 or later.
See remediation →
72/100
Remediation priority · Elevated
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-362

Two operations that should be atomic can interleave, so an attacker who wins a narrow timing window reaches an inconsistent, exploitable state. These bugs are subtle and easy to miss in review. Fixing them properly means correct locking or atomic operations around the shared resource.

General guidance for the race condition class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 3.12, < 6.1.149>= 6.2, < 6.6.103>= 6.7, < 6.12.44>= 6.13, < 6.15.11>= 6.16, < 6.16.2
Debian LinuxOperating system
Affected:= 11.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.1.149 / 6.6.103 / 6.12.44 or later
Fixed in 6.1.1496.6.1036.12.44
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux Kernel 6.1.149 / 6.6.103 / 6.12.44 / 6.15.11 or later (Debian 11 kernel update from Debian security repositories)

  1. Identify the current running kernel version using 'uname -r'
  2. For production systems: plan for a scheduled maintenance window to minimize disruption
  3. Back up critical data before kernel upgrade as a precautionary measure
  4. For Debian 11 systems: apply the latest kernel security updates via 'apt-get update && apt-get upgrade' or 'apt-get dist-upgrade'
  5. For upstream Linux: upgrade to kernel version 6.1.149, 6.6.103, 6.12.44, or 6.15.11 or later depending on your base version
  6. Reboot the system to load the new kernel
  7. Verify the fix is applied by checking the kernel version and confirming the CVE is resolved: 'grep -i 2fd0f5ceb997 /boot/config-*' or checking changelog
Caveat Kernel upgrades may require system reboot and could introduce compatibility issues with third-party kernel modules; test in staging first

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,950. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-39759 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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