CVE-2025-40100

Kernel crash via invalid free-space-tree assertion

Published Oct 30, 2025 · Updated Oct 30, 2025

Assertion failure in affected Linux Btrfs kernels since 4.5 allows local users to crash the kernel while rebuilding a free-space tree. populate_free_space_tree() wrongly asserts that an extent-tree search found a block-group item even when a new empty group has no item yet. Reachability requires local privileges and a Btrfs remount that rebuilds the tree; the failed assertion raises a kernel BUG and interrupts the host.

CVSS severity6.8
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Assertion failure in affected Linux Btrfs kernels since 4.5 allows local users to crash the kernel while rebuilding a free-space tree. populate_free_space_tree() wrongly asserts that an extent-tree search found a block-group item even when a new empty group has no item yet. Reachability requires local privileges and a Btrfs remount that rebuilds the tree; the failed assertion raises a kernel BUG and interrupts the host.

The record

CVE
CVE-2025-40100
Published
Oct 30, 2025
Updated
Oct 30, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 30, 2025CVE publishedPublication date reported by the CVE source.
  2. Oct 30, 2025Record 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=4.5
  2. Affected versionversion=a5ed91828518ab076209266c2bc510adabd078df <289498da343b05c886f19b4269429606f86dd17b
  3. Affected versionversion=a5ed91828518ab076209266c2bc510adabd078df <3fdcfd91b93f930d87843156c7c8cc5fbcf9b144
  4. Affected versionversion=a5ed91828518ab076209266c2bc510adabd078df <4f4b9ca73f84130d9fbb0fc02306ce94ce8bdbe6
  5. Affected versionversion=a5ed91828518ab076209266c2bc510adabd078df <a5a51bf4e9b7354ce7cd697e610d72c1b33fd949
  6. Affected versionversion=a5ed91828518ab076209266c2bc510adabd078df <eb145463f22d7d32d426b29fe9810de9e792b6ba

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.5; version=a5ed91828518ab076209266c2bc510adabd078df <289498da343b05c886f19b4269429606f86dd17b; version=a5ed91828518ab076209266c2bc510adabd078df <3fdcfd91b93f930d87843156c7c8cc5fbcf9b144; version=a5ed91828518ab076209266c2bc510adabd078df <4f4b9ca73f84130d9fbb0fc02306ce94ce8bdbe6; version=a5ed91828518ab076209266c2bc510adabd078df <a5a51bf4e9b7354ce7cd697e610d72c1b33fd949; version=a5ed91828518ab076209266c2bc510adabd078df <eb145463f22d7d32d426b29fe9810de9e792b6ba

Published CVSS scores

5.5Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5OracleCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.8SUSECVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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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

T1499Endpoint Denial of Service

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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