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NVD / CVE Program· CNA Linux

CVE-2025-37856: btrfs: harden block_group::bg_list against list_del() races

MediumCVSS 5.5 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.31% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 185fd73e5ac06027c4be9a129e59193f6a3ef202, 5.16, 6.1.191; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes.
  • Severity is disputed: the assigning authority (CNA) scores it 7.8, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 185fd73e5ac06027c4be9a129e59193f6a3ef202, 5.16, 6.1.191; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published
May 9, 2025
Updated
Oct 30, 2026
EPSS
0.3% · 24th percentile
CWE
—

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CNA vs NVD score

NVD
5.5
CNA · Linux
7.8
2.3 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • edf3b5aadb2515c808200b904baa5b70a727f0ac, 5d19abcffd8404078dfa7d7118cec357b5e7bc58, 6.5affected
    • 01eca70ef8cf499d0cb6d1bbd691558e7792cf17 and later · before ccb20413e7c82e4429c81f10d0e36cd9c0c643cdaffected · git
    • a9f189716cf15913c453299d72f69c51a9b0f86b and later · before 9039afe6240ae01d6caf2fa731590ac74fb8a69baffected · git
    • a9f189716cf15913c453299d72f69c51a9b0f86b and later · before bf089c4d1141b27332c092b1dcca5022c415a3b6affected · git
    • a9f189716cf15913c453299d72f69c51a9b0f86b and later · before 909e60fb469d4101c6b08cf6e622efb062bb24a1affected · git
    • a9f189716cf15913c453299d72f69c51a9b0f86b and later · before 185fd73e5ac06027c4be9a129e59193f6a3ef202affected · git
    • a9f189716cf15913c453299d72f69c51a9b0f86b and later · before 7511e29cf1355b2c47d0effb39e463119913e2f6affected · git
    • 6.1.47 and later · before 6.1.191affected · semver
    • 5.15.128 and later · before 5.16affected · semver
    • 6.4.12 and later · before 6.5affected · semver

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernelbefore 6.12.24
  • linux linux kernel6.13 and later · before 6.13.12
  • linux linux kernel6.14 and later · before 6.14.3

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:13linuxbefore 6.12.25-16.12.25-1
openSUSE:Leap 15.6dtb-aarch64before 6.4.0-150600.23.65.16.4.0-150600.23.65.1
openSUSE:Leap 15.6kernel-64kbbefore 6.4.0-150600.23.65.16.4.0-150600.23.65.1
openSUSE:Leap 15.6kernel-azurebefore 6.4.0-150600.8.48.16.4.0-150600.8.48.1
openSUSE:Leap 15.6kernel-debugbefore 6.4.0-150600.23.65.16.4.0-150600.23.65.1
openSUSE:Leap 15.6kernel-defaultbefore 6.4.0-150600.23.65.16.4.0-150600.23.65.1
openSUSE:Leap 15.6kernel-default-basebefore 6.4.0-150600.23.65.1.150600.12.28.46.4.0-150600.23.65.1.150600.12.28.4
openSUSE:Leap 15.6kernel-docsbefore 6.4.0-150600.23.65.16.4.0-150600.23.65.1
openSUSE:Leap 15.6kernel-kvmsmallbefore 6.4.0-150600.23.65.16.4.0-150600.23.65.1
openSUSE:Leap 15.6kernel-obs-buildbefore 6.4.0-150600.23.65.16.4.0-150600.23.65.1
openSUSE:Leap 15.6kernel-obs-qabefore 6.4.0-150600.23.65.16.4.0-150600.23.65.1
openSUSE:Leap 15.6kernel-rtbefore 6.4.0-150600.10.49.16.4.0-150600.10.49.1
openSUSE:Leap 15.6kernel-rt_debugbefore 6.4.0-150600.10.49.16.4.0-150600.10.49.1
openSUSE:Leap 15.6kernel-sourcebefore 6.4.0-150600.23.65.16.4.0-150600.23.65.1
openSUSE:Leap 15.6kernel-source-azurebefore 6.4.0-150600.8.48.16.4.0-150600.8.48.1
openSUSE:Leap 15.6kernel-source-rtbefore 6.4.0-150600.10.49.16.4.0-150600.10.49.1
openSUSE:Leap 15.6kernel-symsbefore 6.4.0-150600.23.65.16.4.0-150600.23.65.1
openSUSE:Leap 15.6kernel-syms-azurebefore 6.4.0-150600.8.48.16.4.0-150600.8.48.1
openSUSE:Leap 15.6kernel-syms-rtbefore 6.4.0-150600.10.49.16.4.0-150600.10.49.1
openSUSE:Leap 15.6kernel-zfcpdumpbefore 6.4.0-150600.23.65.16.4.0-150600.23.65.1
openSUSE:Leap 16.0dtb-aarch64before 6.12.0-160000.6.16.12.0-160000.6.1
openSUSE:Leap 16.0kernel-64kbbefore 6.12.0-160000.6.16.12.0-160000.6.1
openSUSE:Leap 16.0kernel-defaultbefore 6.12.0-160000.6.16.12.0-160000.6.1

+59

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe…KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2025-37848May 9, 2025 · accel/ivpu: Fix PM related deadlocks in MS IOCTLs
    22Monitor
  • ← EarlierCVE-2025-37853May 9, 2025 · drm/amdkfd: debugfs hang_hws skip GPU with MES
    22Monitor
  • Later →CVE-2025-37857May 9, 2025 · scsi: st: Fix array overflow in st_setup()
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux185fd73e5ac06027c4be9a129e59193f6a3ef202Vendor (CNA)
Linux Linux5.16Vendor (CNA)
Linux Linux6.1.191Vendor (CNA)
Linux Linux6.5Vendor (CNA)
Linux Linux7511e29cf1355b2c47d0effb39e463119913e2f6Vendor (CNA)
Linux Linux9039afe6240ae01d6caf2fa731590ac74fb8a69bVendor (CNA)
Linux Linux909e60fb469d4101c6b08cf6e622efb062bb24a1Vendor (CNA)
Linux Linuxbf089c4d1141b27332c092b1dcca5022c415a3b6Vendor (CNA)
Linux Linuxccb20413e7c82e4429c81f10d0e36cd9c0c643cdVendor (CNA)
azl3 kernel 6.6.150.1-1 on Azure Linux 3.0—Microsoft (MSRC)
azl3 kernel 6.6.152.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0Release NotesMicrosoft (MSRC)
debian:linux6.12.25-1 · Debian:13Package registry (OSV)
opensuse:dtb-aarch646.4.0-150600.23.65.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-64kb6.4.0-150600.23.65.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-azure6.4.0-150600.8.48.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-debug6.4.0-150600.23.65.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-default6.4.0-150600.23.65.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-default-base6.4.0-150600.23.65.1.150600.12.28.4 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-docs6.4.0-150600.23.65.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-kvmsmall6.4.0-150600.23.65.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-obs-build6.4.0-150600.23.65.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-obs-qa6.4.0-150600.23.65.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-source-azure6.4.0-150600.8.48.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:kernel-syms-azure6.4.0-150600.8.48.1 · openSUSE:Leap 15.6Package registry (OSV)
suse:kernel-64kb6.4.0-150600.23.65.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP6Package registry (OSV)
suse:kernel-azure6.4.0-150600.8.48.1 · SUSE:Linux Enterprise Module for Public Cloud 15 SP6Package registry (OSV)
suse:kernel-default6.4.0-150600.23.65.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP6Package registry (OSV)
suse:kernel-default-base6.4.0-150600.23.65.1.150600.12.28.4 · SUSE:Linux Enterprise Module for Basesystem 15 SP6Package registry (OSV)

+9

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

—

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records