CVE-2025-21926

Local kernel crash via stale socket ownership

Published Apr 1, 2025 · Updated Sep 8, 2026

Improper input validation in affected Linux kernel builds allows local users to crash the kernel through OpenVSwitch packet actions. __udp_gso_segment clears an skb destructor but retains its socket reference, leaving inconsistent ownership when the original buffer is later orphaned. The crash requires OpenVSwitch to process a userspace action before an output action; Siemens embeds the affected subsystem in specified controllers.

CVSS severity5.5
Medium
EPSS probability0.24%
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 affected Linux kernel builds allows local users to crash the kernel through OpenVSwitch packet actions. __udp_gso_segment clears an skb destructor but retains its socket reference, leaving inconsistent ownership when the original buffer is later orphaned. The crash requires OpenVSwitch to process a userspace action before an output action; Siemens embeds the affected subsystem in specified controllers.

The record

CVE
CVE-2025-21926
Published
Apr 1, 2025
Updated
Sep 8, 2026
Vendor
Siemens
Product
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
Classifications
CWE-20, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 8, 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=V3.1.6 <*

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Siemens · SIPLUS S7-1500 CPU 1518-4 PN/DP MFPversion=V3.1.6 <*
The Linux Kernel Organization · Linuxversion=4.18; version=ad405857b174ed31a97982bb129c320d03321cf5 <01a83237644d6822bc7df2c5564fc81b0df84358; version=ad405857b174ed31a97982bb129c320d03321cf5 <084819b0d8b1bd433b90142371eb9450d657f8ca; version=ad405857b174ed31a97982bb129c320d03321cf5 <455217ac9db0cf9349b3933664355e907bb1a569; version=ad405857b174ed31a97982bb129c320d03321cf5 <9f28205ddb76e86cac418332e952241d85fed0dc; version=ad405857b174ed31a97982bb129c320d03321cf5 <a2d1cca955ed34873e524cc2e6e885450d262f05; version=ad405857b174ed31a97982bb129c320d03321cf5 <c32da44cc9298eaa6109e3fc2c2b4e07cc4bf11b; version=ad405857b174ed31a97982bb129c320d03321cf5 <e8db70537878e1bb3fd83e5abcc6feefc0587828; version=ad405857b174ed31a97982bb129c320d03321cf5 <ee01b2f2d7d0010787c2343463965bbc283a497f
Siemens · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPversion=V3.1.6 <*
Siemens · SIMATIC S7-1500 CPU 1518-4 PN/DP MFPversion=V3.1.6 <*

Published CVSS scores

5.5Siemens ProductCERTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-20Improper Input Validation
T1499.004Application or System Exploitation

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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