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Linux KernelOperating system · Linux

CVE-2025-37856

MEDIUM · 5.5 CVSS v3.1 Published 2025-05-09
Fix available
A fix is available. Upgrade to 6.12.24 / 6.13.12 or later.
See remediation →
57/100
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: harden block_group::bg_list against list_del() races As far as I can tell, these calls of list_del_init() on bg_list cannot run concurrently with btrfs_mark_bg_unused() or btrfs_mark_bg_to_reclaim(), as they are in transaction error paths and situations where the block group is readonly. However, if there is any chance at all of racing with mark_bg_unused(), or a different future user of bg_list, better to be safe than sorry. Otherwise we risk the following interleaving (bg_list refcount in parens) T1 (some random op) T2 (btrfs_mark_bg_unused) !list_empty(&bg->bg_list); (1) list_del_init(&bg->bg_list); (1) list_move_tail (1) btrfs_put_block_group (0) btrfs_delete_unused_bgs bg = list_first_entry list_del_init(&bg->bg_list); btrfs_put_block_group(bg); (-1) Ultimately, this results in a broken ref count that hits zero one deref early and the real final deref underflows the refcount, resulting in a WARNING.

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

A detailed technical summary for this CVE is being prepared.

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:< 6.12.24>= 6.13, < 6.13.12>= 6.14, < 6.14.3

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
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 6.12.24 / 6.13.12 / 6.14.3 or later
Fixed in 6.12.246.13.126.14.3
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux Kernel 6.12.24, 6.13.12, or 6.14.3 (depending on which major version branch you are on)

  1. Check current kernel version: uname -r
  2. Identify your distribution and its kernel update mechanism (e.g., apt-get update && apt-get upgrade for Debian/Ubuntu, dnf update for Fedora/RHEL, pacman -Syu for Arch)
  3. Update the Linux kernel to version 6.12.24 or higher if running 6.12.x
  4. If running Linux 6.13.x, upgrade to version 6.13.12 or higher
  5. If running Linux 6.14.x, upgrade to version 6.14.3 or higher
  6. Reboot the system to load the new kernel: systemctl reboot
  7. Verify the fix is applied by checking the kernel version after reboot: uname -r
Caveat Standard kernel upgrade risks apply; minor version upgrades within the same branch are generally low-risk but test in non-production environments 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 $1,600. 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-2025-37856 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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