CVE-2025-21763

Kernel memory corruption via unprotected neighbour notification

Published Feb 27, 2025 · Updated Aug 5, 2026

Use-after-free in Linux kernel neighbour notifications allows local users to corrupt kernel memory through a network-namespace race. __neigh_notify() dereferences a device's network namespace without RTNL or an RCU read-side critical section while concurrent teardown can free it. Reaching the race requires low-privilege local syscall access to create and migrate network namespaces; a successful race can crash the system or corrupt kernel state.

CVSS severity7.8
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux kernel neighbour notifications allows local users to corrupt kernel memory through a network-namespace race. __neigh_notify() dereferences a device's network namespace without RTNL or an RCU read-side critical section while concurrent teardown can free it. Reaching the race requires low-privilege local syscall access to create and migrate network namespaces; a successful race can crash the system or corrupt kernel state.

The record

CVE
CVE-2025-21763
Published
Feb 27, 2025
Updated
Aug 5, 2026
Vendor
Siemens
Product
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
Classifications
CWE-416, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 27, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=0 <*

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Siemens · SIMATIC S7-1500 TM MFP - GNU/Linux subsystemversion=0 <*
The Linux Kernel Organization · Linuxversion=2.6.25; version=426b5303eb435d98b9bee37a807be386bc2b3320 <1cbb2aa90cd3fba15ad7efb5cdda28f3d1082379; version=426b5303eb435d98b9bee37a807be386bc2b3320 <40d8f2f2a373b6c294ffac394d2bb814b572ead1; version=426b5303eb435d98b9bee37a807be386bc2b3320 <559307d25235e24b5424778c7332451b6c741159; version=426b5303eb435d98b9bee37a807be386bc2b3320 <784eb2376270e086f7db136d154b8404edacf97b; version=426b5303eb435d98b9bee37a807be386bc2b3320 <8666e9aab801328c1408a19fbf4070609dc0695a; version=426b5303eb435d98b9bee37a807be386bc2b3320 <becbd5850c03ed33b232083dd66c6e38c0c0e569; version=426b5303eb435d98b9bee37a807be386bc2b3320 <cdd5c2a12ddad8a77ce1838ff9f29aa587de82df; version=426b5303eb435d98b9bee37a807be386bc2b3320 <e1aed6be381bcd7f46d4ca9d7ef0f5f3d6a1be32

Published CVSS scores

5.5Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.8CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8Siemens ProductCERTCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 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-416Use After Free
T1068Exploitation for Privilege Escalation

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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