CVE-2025-21875

Local system crash via unlocked MPTCP address removal

Published Mar 27, 2025 · Updated Sep 8, 2026

Race condition in the MPTCP path manager in Linux kernel builds and Siemens firmware V3.1.6 allows local users to crash the system. The address-removal path can send RM_ADDR from mptcp_pm_nl_addr_send_ack without holding the MPTCP socket lock while another process changes subflows, enabling stale subflow access. Reaching the path requires local low-privileged access and concurrent MPTCP netlink and subflow operations; no remote peer can trigger it alone.

CVSS severity7.8
High
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in the MPTCP path manager in Linux kernel builds and Siemens firmware V3.1.6 allows local users to crash the system. The address-removal path can send RM_ADDR from mptcp_pm_nl_addr_send_ack without holding the MPTCP socket lock while another process changes subflows, enabling stale subflow access. Reaching the path requires local low-privileged access and concurrent MPTCP netlink and subflow operations; no remote peer can trigger it alone.

The record

CVE
CVE-2025-21875
Published
Mar 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. Mar 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=5.10; version=b6c08380860b926752d57c8fa9911fa388c4b876 <2c3de6dff4373f1036e003f49a32629359530bdb; version=b6c08380860b926752d57c8fa9911fa388c4b876 <4124b782ec2b1e2e490cf0bbf10f53dfd3479890; version=b6c08380860b926752d57c8fa9911fa388c4b876 <494ec285535632732eaa5786297a9ae4f731b5ff; version=b6c08380860b926752d57c8fa9911fa388c4b876 <7cca31035c05819643ffb5d7518e9a331b3f6651; version=b6c08380860b926752d57c8fa9911fa388c4b876 <8116fb4acd5d3f06cd37f84887dbe962b6703b1c; version=b6c08380860b926752d57c8fa9911fa388c4b876 <a05da2be18aae7e82572f8d795f41bb49f5dfc7d; version=b6c08380860b926752d57c8fa9911fa388c4b876 <f865c24bc55158313d5779fc81116023a6940ca3
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

7.8Linux Kernel CVE TeamCVSS: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.

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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