CVE-2021-33627

SMM code execution via unchecked communication buffer

Published Feb 3, 2022 · Updated Aug 11, 2026

Memory validation failure in InsydeH2O 5.x on Siemens industrial PCs allows local users to reach protected memory through an SMI. FwBlockServiceSmm passes an unchecked EFI_SMM_COMMUNICATION_PROTOCOL buffer address to software SMI services, permitting SMRAM, MMIO, or kernel addresses. The caller needs high local privileges; successful abuse can corrupt protected memory and execute code with SMM privileges.

CVSS severity8.2

High

EPSS probability0.33%

Next 30 days · Sep 17, 2026

Known exploitationUnconfirmed

Based on sourced intelligence

Hinoki checkNot available

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Summary

What happened

The record

CVE: CVE-2021-33627
Published: Feb 3, 2022
Updated: Aug 11, 2026

Vendor: Siemens
Product: SIMATIC IPC477E PRO
Classifications: CWE-119, T1068

Attack vector: local
Privileges: admin

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 privilegesadmin

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

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

8.2Siemens ProductCERTCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

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

Privilegesadmin

Known exploitationUnconfirmed

Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer

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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