CVE-2025-39736

System hang via kmemleak netpoll lock inversion

Published Sep 11, 2025 · Updated May 12, 2026

Deadlock in the Linux kernel and SIMATIC CN 4100 before 5.0 allows local users to hang affected systems through a lock inversion. In mem_pool_alloc(), pr_warn_once() runs while kmemleak_lock is held; netpoll then allocates an skb and reenters kmemleak to acquire the same lock. Reachability requires local low-privileged access plus enabled netpoll and kmemleak; no confidentiality or integrity impact is reported.

CVSS severity5.5
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Deadlock in the Linux kernel and SIMATIC CN 4100 before 5.0 allows local users to hang affected systems through a lock inversion. In mem_pool_alloc(), pr_warn_once() runs while kmemleak_lock is held; netpoll then allocates an skb and reenters kmemleak to acquire the same lock. Reachability requires local low-privileged access plus enabled netpoll and kmemleak; no confidentiality or integrity impact is reported.

The record

CVE
CVE-2025-39736
Published
Sep 11, 2025
Updated
May 12, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-833, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 11, 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=5.4
  2. Affected versionversion=c5665868183fec689dbab9fb8505188b2c4f0757 <08f70be5e406ce47c822f2dd11c1170ca259605b
  3. Affected versionversion=c5665868183fec689dbab9fb8505188b2c4f0757 <1da95d3d4b7b1d380ebd87b71a61e7e6aed3265d
  4. Affected versionversion=c5665868183fec689dbab9fb8505188b2c4f0757 <47b0f6d8f0d2be4d311a49e13d2fd5f152f492b2
  5. Affected versionversion=c5665868183fec689dbab9fb8505188b2c4f0757 <4b0151e1d468eb2667c37b7af99b3c075072d334
  6. Affected versionversion=c5665868183fec689dbab9fb8505188b2c4f0757 <62879faa8efe8d8a9c7bf7606ee9c068012d7dac
  7. Affected versionversion=c5665868183fec689dbab9fb8505188b2c4f0757 <a0854de00ce2ee27edf39037e7836ad580eb3350
  8. Affected versionversion=c5665868183fec689dbab9fb8505188b2c4f0757 <a181b228b37a6a5625dad2bb4265bb7abb673e9f
  9. Affected versionversion=c5665868183fec689dbab9fb8505188b2c4f0757 <c7b6ea0ede687e7460e593c5ea478f50aa41682a
  10. Affected versionversion=c5665868183fec689dbab9fb8505188b2c4f0757 <f249d32bb54876b4b6c3ae071af8ddca77af390b

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.4; version=c5665868183fec689dbab9fb8505188b2c4f0757 <08f70be5e406ce47c822f2dd11c1170ca259605b; version=c5665868183fec689dbab9fb8505188b2c4f0757 <1da95d3d4b7b1d380ebd87b71a61e7e6aed3265d; version=c5665868183fec689dbab9fb8505188b2c4f0757 <47b0f6d8f0d2be4d311a49e13d2fd5f152f492b2; version=c5665868183fec689dbab9fb8505188b2c4f0757 <4b0151e1d468eb2667c37b7af99b3c075072d334; version=c5665868183fec689dbab9fb8505188b2c4f0757 <62879faa8efe8d8a9c7bf7606ee9c068012d7dac; version=c5665868183fec689dbab9fb8505188b2c4f0757 <a0854de00ce2ee27edf39037e7836ad580eb3350; version=c5665868183fec689dbab9fb8505188b2c4f0757 <a181b228b37a6a5625dad2bb4265bb7abb673e9f; version=c5665868183fec689dbab9fb8505188b2c4f0757 <c7b6ea0ede687e7460e593c5ea478f50aa41682a; version=c5665868183fec689dbab9fb8505188b2c4f0757 <f249d32bb54876b4b6c3ae071af8ddca77af390b
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 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-833Deadlock
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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