CVE-2025-21913

Kernel warning via unsafe Xen MSR read

Published Apr 1, 2025 · Updated Sep 8, 2026

Improper MSR access in the Linux kernel allows local users in affected Xen guests to encounter an unchecked-read warning during boot. amd_get_mmconfig_range() directly reads MSR_FAM10H_MMIO_CONF_BASE even when Xen has not exposed that register to the guest. The condition requires a Xen guest with the missing MSR and a PNP0c01-device quirk; MMCFG remains disabled after the warning.

CVSS severity5.3
Medium
EPSS probability0.20%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper MSR access in the Linux kernel allows local users in affected Xen guests to encounter an unchecked-read warning during boot. amd_get_mmconfig_range() directly reads MSR_FAM10H_MMIO_CONF_BASE even when Xen has not exposed that register to the guest. The condition requires a Xen guest with the missing MSR and a PNP0c01-device quirk; MMCFG remains disabled after the warning.

The record

CVE
CVE-2025-21913
Published
Apr 1, 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. Apr 1, 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=3fac3734c43a2e21fefeb72124d8bd31dff3956f <0c65d13bdcc54e5b924ebe790f85a7f01bfe1cb1; version=3fac3734c43a2e21fefeb72124d8bd31dff3956f <14cb5d83068ecf15d2da6f7d0e9ea9edbcbc0457; version=3fac3734c43a2e21fefeb72124d8bd31dff3956f <8f43ba5ee498fe037d1570f6868d9aeaf49dda80; version=3fac3734c43a2e21fefeb72124d8bd31dff3956f <923fede9eae9865af305bcdf8f111e4b62ae4bda; version=3fac3734c43a2e21fefeb72124d8bd31dff3956f <ebf6a763904e42dabeb2e270ceb0bbe0f825d7ae; version=6.1
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

5.3Siemens ProductCERTCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L

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 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

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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