CVE-2025-37856

Kernel memory corruption via bg_list refcount race

Published May 9, 2025 · Updated Aug 5, 2026

A btrfs block-group race in the Linux kernel allows local users to corrupt kernel memory through ordinary file operations. Concurrent list_del_init() and list_move_tail() operations on block_group::bg_list can let btrfs_put_block_group() free a block group while it remains linked on the unused list. Exploitation requires write access to a locally mounted btrfs filesystem and can expose or corrupt kernel heap data, panic the system, or damage filesystem metadata.

CVSS severity7.8
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A btrfs block-group race in the Linux kernel allows local users to corrupt kernel memory through ordinary file operations. Concurrent list_del_init() and list_move_tail() operations on block_group::bg_list can let btrfs_put_block_group() free a block group while it remains linked on the unused list. Exploitation requires write access to a locally mounted btrfs filesystem and can expose or corrupt kernel heap data, panic the system, or damage filesystem metadata.

The record

CVE
CVE-2025-37856
Published
May 9, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 9, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=01eca70ef8cf499d0cb6d1bbd691558e7792cf17
  2. Affected versionversion=5.15.128 <5.16
  3. Affected versionversion=5d19abcffd8404078dfa7d7118cec357b5e7bc58
  4. Affected versionversion=6.1.47 <6.2
  5. Affected versionversion=6.4.12 <6.5
  6. Affected versionversion=6.5
  7. Affected versionversion=a9f189716cf15913c453299d72f69c51a9b0f86b <185fd73e5ac06027c4be9a129e59193f6a3ef202
  8. Affected versionversion=a9f189716cf15913c453299d72f69c51a9b0f86b <7511e29cf1355b2c47d0effb39e463119913e2f6
  9. Affected versionversion=a9f189716cf15913c453299d72f69c51a9b0f86b <909e60fb469d4101c6b08cf6e622efb062bb24a1
  10. Affected versionversion=a9f189716cf15913c453299d72f69c51a9b0f86b <bf089c4d1141b27332c092b1dcca5022c415a3b6
  11. Affected versionversion=edf3b5aadb2515c808200b904baa5b70a727f0ac

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=01eca70ef8cf499d0cb6d1bbd691558e7792cf17; version=5.15.128 <5.16; version=5d19abcffd8404078dfa7d7118cec357b5e7bc58; version=6.1.47 <6.2; version=6.4.12 <6.5; version=6.5; version=a9f189716cf15913c453299d72f69c51a9b0f86b <185fd73e5ac06027c4be9a129e59193f6a3ef202; version=a9f189716cf15913c453299d72f69c51a9b0f86b <7511e29cf1355b2c47d0effb39e463119913e2f6; version=a9f189716cf15913c453299d72f69c51a9b0f86b <909e60fb469d4101c6b08cf6e622efb062bb24a1; version=a9f189716cf15913c453299d72f69c51a9b0f86b <bf089c4d1141b27332c092b1dcca5022c415a3b6; version=edf3b5aadb2515c808200b904baa5b70a727f0ac

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.8kernel.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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

T1068Exploitation for Privilege Escalation

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

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Your stack

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