CVE-2025-21706

Local service interruption via permissive fullmesh flagging

Published Feb 27, 2025 · Updated Sep 8, 2026

Improper input validation in Linux kernel MPTCP path management allows local users to interrupt service by changing endpoint flags. The set_flags() hook accepts the fullmesh flag for implicit endpoints even though mptcp_pm_nl_fullmesh() expects only subflow endpoints. A local user able to issue the MPTCP generic-netlink flag change can reach a kernel warning path with high availability impact.

CVSS severity5.5
Medium
EPSS probability0.21%
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 Linux kernel MPTCP path management allows local users to interrupt service by changing endpoint flags. The set_flags() hook accepts the fullmesh flag for implicit endpoints even though mptcp_pm_nl_fullmesh() expects only subflow endpoints. A local user able to issue the MPTCP generic-netlink flag change can reach a kernel warning path with high availability impact.

The record

CVE
CVE-2025-21706
Published
Feb 27, 2025
Updated
Sep 8, 2026
Vendor
Siemens
Product
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
Classifications
CWE-20
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=V3.1.6 <*

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=5.18; version=73c762c1f07dacba4fd1cefd15e24b419d42320d <1bb0d1348546ad059f55c93def34e67cb2a034a6; version=73c762c1f07dacba4fd1cefd15e24b419d42320d <22b0734c9401a74ed4ebd9e8ef0da33e493852eb; version=73c762c1f07dacba4fd1cefd15e24b419d42320d <8ac344cbd84fda75e05e1f445f7f8fb24dc175e1; version=73c762c1f07dacba4fd1cefd15e24b419d42320d <9e3d61620a3cd033319553b980ff3a350adbe1bc; version=73c762c1f07dacba4fd1cefd15e24b419d42320d <de3b8d41d2547452c4cafb146d003fa4689fbaf2
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

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 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

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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