CVE-2025-37856

Medium

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.

Package Linux Kernel
Published 2025-05-09
Last modified 2025-11-12
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

5.5

out of 10
Medium
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected versions

Linux kernel versions 5.15.128, 6.1.47, 6.4.12, 6.5 and later are affected. Fixed in 6.12.24, 6.13.12, 6.14.3, 6.15 and their respective stable series.

Affected from
≥ 5.15.128 ≥ 6.1.47 ≥ 6.4.12 ≥ 6.5
Fixed in
✓ 6.12.24 6.12.x ✓ 6.13.12 6.13.x ✓ 6.14.3 6.14.x ✓ 6.15

References

The following references provide additional information about CVE-2025-37856 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

4 patch commits total View all on NVD

Frequently asked questions

  • What is CVE-2025-37856?

    CVE-2025-37856 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 . It affects Linux kernel versions from 5.15.128 onward and has been patched in 6.12.24, 6.13.12, 6.14.3 and others. CVE-2025-37856 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2025-37856?

    CVE-2025-37856 has a CVSS score of 5.5 out of 10, rated Medium severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H .

  • Is there a patch available for CVE-2025-37856?

    Yes — CVE-2025-37856 has been patched. Fixed versions include 6.12.24, 6.13.12, 6.14.3 and others. If you are running Linux kernel 5.15.128 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2025-37856 actively exploited?

    No — CVE-2025-37856 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

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