CVE-2025-38711

SMB service hang via recursive parent locking

Published Sep 4, 2025 · Updated May 12, 2026

Improper locking in Linux ksmbd allows local users to hang SMB service; SIMATIC CN 4100 before 5.0 is also affected. The ReplaceIfExists path removes an existing link while retaining the parent-directory lock, then ksmbd_vfs_link() tries to acquire that same lock and deadlocks. Low-privileged access to a configured ksmbd share and an existing destination name are required; the deadlock interrupts SMB file service.

CVSS severity5.5
Medium
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper locking in Linux ksmbd allows local users to hang SMB service; SIMATIC CN 4100 before 5.0 is also affected. The ReplaceIfExists path removes an existing link while retaining the parent-directory lock, then ksmbd_vfs_link() tries to acquire that same lock and deadlocks. Low-privileged access to a configured ksmbd share and an existing destination name are required; the deadlock interrupts SMB file service.

The record

CVE
CVE-2025-38711
Published
Sep 4, 2025
Updated
May 12, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-667, CWE-20, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 4, 2025CVE publishedPublication date reported by the CVE source.
  2. May 12, 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=0626e6641f6b467447c81dd7678a69c66f7746cf <1e858a7a51c7b8b009d8f246de7ceb7743b44a71
  2. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <814cfdb6358d9b84fcbec9918c8f938cc096a43a
  3. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <9d5012ffe14120f978ee34aef4df3d6cb026b7c4
  4. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <a726fef6d7d4cfc365d3434e3916dbfe78991a33
  5. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <a7dddd62578c2eb6cb28b8835556a121b5157323
  6. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <ac98d54630d5b52e3f684d872f0d82c06c418ea9
  7. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <d5fc1400a34b4ea5e8f2ce296ea12bf8c8421694
  8. Affected versionversion=5.15

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=0626e6641f6b467447c81dd7678a69c66f7746cf <1e858a7a51c7b8b009d8f246de7ceb7743b44a71; version=0626e6641f6b467447c81dd7678a69c66f7746cf <814cfdb6358d9b84fcbec9918c8f938cc096a43a; version=0626e6641f6b467447c81dd7678a69c66f7746cf <9d5012ffe14120f978ee34aef4df3d6cb026b7c4; version=0626e6641f6b467447c81dd7678a69c66f7746cf <a726fef6d7d4cfc365d3434e3916dbfe78991a33; version=0626e6641f6b467447c81dd7678a69c66f7746cf <a7dddd62578c2eb6cb28b8835556a121b5157323; version=0626e6641f6b467447c81dd7678a69c66f7746cf <ac98d54630d5b52e3f684d872f0d82c06c418ea9; version=0626e6641f6b467447c81dd7678a69c66f7746cf <d5fc1400a34b4ea5e8f2ce296ea12bf8c8421694; version=5.15
Siemens · SIMATIC CN 4100version=0 <V5.0

Published CVSS scores

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

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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

CWE-667Improper Locking
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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