CVE-2025-21707

Service interruption via stale MPTCP suboption state

Published Feb 27, 2025 · Updated Sep 8, 2026

Use of uninitialized MPTCP data in Linux and Siemens controller firmware allows local users to interrupt service through stale state. The option parser clears its received-suboption bitmask without clearing corresponding per-suboption bitfields, so __mptcp_expand_seq consumes uninitialized status during incoming-option processing. Low-privileged local access and a reachable MPTCP path are required; the reported consequence is limited to service availability, with no data disclosure or modification.

CVSS severity5.5
Medium
EPSS probability0.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use of uninitialized MPTCP data in Linux and Siemens controller firmware allows local users to interrupt service through stale state. The option parser clears its received-suboption bitmask without clearing corresponding per-suboption bitfields, so __mptcp_expand_seq consumes uninitialized status during incoming-option processing. Low-privileged local access and a reachable MPTCP path are required; the reported consequence is limited to service availability, with no data disclosure or modification.

The record

CVE
CVE-2025-21707
Published
Feb 27, 2025
Updated
Sep 8, 2026
Vendor
Siemens
Product
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
Classifications
CWE-908, 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=V3.1.6 <*

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=5.11; version=84dfe3677a6f45b3d0dfdd564e55717a1a5e60cc <3a7fda57b0f91f7ea34476b165f91a92feb17c96; version=84dfe3677a6f45b3d0dfdd564e55717a1a5e60cc <3b5332d416d151a15742d1b16e7319368e3cc5c6; version=84dfe3677a6f45b3d0dfdd564e55717a1a5e60cc <6169e942370b4b6f9442d35c51519bf6c346843b; version=84dfe3677a6f45b3d0dfdd564e55717a1a5e60cc <7f6c72b8ef8130760710e337dc8fbe7263954884; version=84dfe3677a6f45b3d0dfdd564e55717a1a5e60cc <ba0518f9e8688cd4fcb569e8df2a74874b4f3894; version=84dfe3677a6f45b3d0dfdd564e55717a1a5e60cc <c86b000782daba926c627d2fa00c3f60a75e7472
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.

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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-908Use of Uninitialized Resource
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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