CVE-2021-42554

SMM privilege escalation via out-of-bounds write

Published Feb 3, 2022 · Updated Aug 11, 2026

SMM memory corruption in InsydeH2O firmware allows local users to gain SMM privileges by writing fixed or predictable data to SMRAM. In FvbServicesRuntimeDxe, an out-of-bounds write corrupts SMM memory by placing fixed or predictable data in protected SMRAM. Local code execution on an affected device is required, and successful exploitation crosses into SMM with control beyond the operating system.

CVSS severity8.4

High

EPSS probability0.33%

Next 30 days · Sep 16, 2026

Known exploitationUnconfirmed

Based on sourced intelligence

Hinoki checkNot available

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Summary

What happened

The record

CVE: CVE-2021-42554
Published: Feb 3, 2022
Updated: Aug 11, 2026

Vendor: Siemens
Product: SIMATIC IPC477E PRO
Classifications: CWE-787, T1068

Attack vector: local
Privileges: unauthenticated

Timeline

How it unfolded

Feb 3, 2022CVE publishedPublication date reported by the CVE source.
Aug 11, 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.

Affected versionversion=0 <V21.01.17

What conditions does exploitation require?

Attack vectorlocal

Required privilegesunauthenticated

What is affected?

Siemens · SIMATIC IPC477E PROversion=0 <V21.01.17

Siemens · SIMATIC IPC847Eversion=0 <V25.02.12

Siemens · SIMATIC Field PG M5version=0 <V22.01.10

Siemens · SIMATIC IPC377Gversion=0 <V28.01.04

Siemens · RUGGEDCOM APE1808 BIOSversion=0 <V1.0.202N

Siemens · SIMATIC IPC627Eversion=0 <V25.02.12

Siemens · SIMATIC IPC277Gversion=0 <V28.01.04

Siemens · SIMATIC ITP1000version=0 <V23.01.10

Siemens · SIMATIC IPC677Eversion=0 <V25.02.12

Siemens · SIMATIC IPC127E Industrial Edge Deviceversion=0 <V27.01.09

Siemens · SIMATIC IPC427E Industrial Edge Deviceversion=0 <V21.01.17

Siemens · SIMATIC IPC477Eversion=0 <V21.01.17

Siemens · SIMATIC IPC277G PROversion=0 <V28.01.04

Siemens · SIMATIC IPC227G Industrial Edge Deviceversion=0 <V28.01.04

Siemens · SIMATIC IPC327Gversion=0 <V28.01.04

Siemens · SIMATIC IPC647Eversion=0 <V25.02.12

Siemens · SIPLUS IPC427Eversion=0 <V21.01.17

Siemens · SIMATIC Field PG M6version=0 <V26.01.13

Published CVSS scores

8.4Siemens ProductCERTCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

7.2NIST NVDAV:L/AC:L/Au:N/C:C/I:C/A:C

8.2NIST NVDCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/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.

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

Privilegesunauthenticated

Known exploitationUnconfirmed

Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write

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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