CVE-2025-21999

Kernel crash via stale proc_ops dereference

Published Apr 3, 2025 · Updated Sep 8, 2026

Use-after-free in Linux proc_get_inode() allows local users to crash the kernel by racing module removal with /proc inode lookup. The function dereferences module-owned pde->proc_ops after rmmod frees the module while another task instantiates a /proc inode. Reaching the flaw requires local access and concurrent module removal; the published execution trace ends in a kernel page fault.

CVSS severity7.8
High
EPSS probability0.23%
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 proc_get_inode() allows local users to crash the kernel by racing module removal with /proc inode lookup. The function dereferences module-owned pde->proc_ops after rmmod frees the module while another task instantiates a /proc inode. Reaching the flaw requires local access and concurrent module removal; the published execution trace ends in a kernel page fault.

The record

CVE
CVE-2025-21999
Published
Apr 3, 2025
Updated
Sep 8, 2026
Vendor
Siemens
Product
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
Classifications
CWE-416, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 3, 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=5.6; version=97a32539b9568bb653683349e5a76d02ff3c3e2c <4b0b8445b6fd41e6f62ac90547a0ea9d348de3fa; version=97a32539b9568bb653683349e5a76d02ff3c3e2c <63b53198aff2e4e6c5866a4ff73c7891f958ffa4; version=97a32539b9568bb653683349e5a76d02ff3c3e2c <64dc7c68e040251d9ec6e989acb69f8f6ae4a10b; version=97a32539b9568bb653683349e5a76d02ff3c3e2c <654b33ada4ab5e926cd9c570196fefa7bec7c1df; version=97a32539b9568bb653683349e5a76d02ff3c3e2c <966f331403dc3ed04ff64eaf3930cf1267965e53; version=97a32539b9568bb653683349e5a76d02ff3c3e2c <eda279586e571b05dff44d48e05f8977ad05855d; version=97a32539b9568bb653683349e5a76d02ff3c3e2c <ede3e8ac90ae106f0b29cd759aadebc1568f1308
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

7.8CISA-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 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-416Use After Free
T1499Endpoint Denial of Service

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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