CVE-2025-39738

Filesystem corruption via partially dropped subvolume relocation

Published Sep 11, 2025 · Updated Aug 5, 2026

Improper input validation in Btrfs relocation in Linux and SIMATIC CN 4100 before 5.0 allows local users to corrupt filesystem data. The relocation path accepts a root item with nonzero drop_progress but no orphan item, then drops already-removed extent references. A crafted Btrfs image and relocation through balance or background reclaim are required; the result can corrupt files and force the filesystem read-only.

CVSS severity7.3
High
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Btrfs relocation in Linux and SIMATIC CN 4100 before 5.0 allows local users to corrupt filesystem data. The relocation path accepts a root item with nonzero drop_progress but no orphan item, then drops already-removed extent references. A crafted Btrfs image and relocation through balance or background reclaim are required; the result can corrupt files and force the filesystem read-only.

The record

CVE
CVE-2025-39738
Published
Sep 11, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-20, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 11, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=5.11
  2. Affected versionversion=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <125e94a4b76b7b75d194f85bedd628097d2121f0
  3. Affected versionversion=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <39a93e1c9dbf7e11632efeb20fcf0fc1dcf64d51
  4. Affected versionversion=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <4289b494ac553e74e86fed1c66b2bf9530bc1082
  5. Affected versionversion=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <4e403bd8e127d40dc7c05f06ee969c1ba1537ec5
  6. Affected versionversion=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <f83d4c81bda3b7d1813268ab77408f7a0ce691ff
  7. Affected versionversion=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <fa086b1398cf7e5f7dee7241bd5f2855cb5df8dc
  8. Affected versionversion=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <fcb1f77b8ed8795608ca7a1f6505e2b07236c1f3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.11; version=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <125e94a4b76b7b75d194f85bedd628097d2121f0; version=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <39a93e1c9dbf7e11632efeb20fcf0fc1dcf64d51; version=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <4289b494ac553e74e86fed1c66b2bf9530bc1082; version=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <4e403bd8e127d40dc7c05f06ee969c1ba1537ec5; version=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <f83d4c81bda3b7d1813268ab77408f7a0ce691ff; version=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <fa086b1398cf7e5f7dee7241bd5f2855cb5df8dc; version=638331fa56caeaa8b4d31cc1dfbe0ce989bcff67 <fcb1f77b8ed8795608ca7a1f6505e2b07236c1f3
Siemens · SIMATIC CN 4100version=0 <V5.0

Published CVSS scores

7.3LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H
5.5Siemens ProductCERTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
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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