CVE-2025-21758

Kernel service interruption via unprotected multicast socket access

Published Feb 27, 2025 · Updated Sep 8, 2026

Improper synchronization in the Linux IPv6 multicast subsystem allows local users to interrupt service through mld_newpack(). The function dereferences and charges net->ipv6.igmp_sk without holding RTNL or an RCU read lock, so the socket can disappear during access. Reachability requires local low-privileged execution, and the affected code is also present in the additional GNU/Linux subsystem of specified Siemens controllers.

CVSS severity7.8
High
EPSS probability13.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper synchronization in the Linux IPv6 multicast subsystem allows local users to interrupt service through mld_newpack(). The function dereferences and charges net->ipv6.igmp_sk without holding RTNL or an RCU read lock, so the socket can disappear during access. Reachability requires local low-privileged execution, and the affected code is also present in the additional GNU/Linux subsystem of specified Siemens controllers.

The record

CVE
CVE-2025-21758
Published
Feb 27, 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. Feb 27, 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

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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=V3.1.5 <*
  2. 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=V3.1.5 <*; version=V3.1.6 <*
The Linux Kernel Organization · Linuxversion=2.6.26; version=b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 <1b91c597b0214b1b462eb627ec02658c944623f2; version=b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 <25195f9d5ffcc8079ad743a50c0409dbdc48d98a; version=b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 <29fa42197f26a97cde29fa8c40beddf44ea5c8f3; version=b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 <a527750d877fd334de87eef81f1cb5f0f0ca3373; version=b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 <d60d493b0e65647e0335e6a7c4547abcea7df8e9; version=b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 <e8af3632a7f2da83e27b083f787bced1faba00b1
Siemens · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPversion=V3.1.5 <*; version=V3.1.6 <*
Siemens · SIMATIC S7-1500 CPU 1518-4 PN/DP MFPversion=V3.1.5 <*; version=V3.1.6 <*

Published CVSS scores

7.8Linux CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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 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.

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Technologies

Your stack

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Your stack

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