CVE-2021-33625

SMM privilege escalation via unchecked communication buffer

Published Feb 3, 2022 · Updated Aug 11, 2026

SMM memory corruption in Siemens industrial PCs with InsydeH2O allows local users with high privileges to execute code in SMM. The HddPassword software SMI service passes an EFI_SMM_COMMUNICATION_PROTOCOL buffer to Communicate() without validating that its address excludes SMRAM, MMIO, and OS kernel memory. Exploitation requires local high privileges and crafted buffer control, and successful corruption grants execution above the operating-system kernel.

CVSS severity8.2
High
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SMM memory corruption in Siemens industrial PCs with InsydeH2O allows local users with high privileges to execute code in SMM. The HddPassword software SMI service passes an EFI_SMM_COMMUNICATION_PROTOCOL buffer to Communicate() without validating that its address excludes SMRAM, MMIO, and OS kernel memory. Exploitation requires local high privileges and crafted buffer control, and successful corruption grants execution above the operating-system kernel.

The record

CVE
CVE-2021-33625
Published
Feb 3, 2022
Updated
Aug 11, 2026
Vendor
Siemens
Product
SIMATIC IPC477E PRO
Classifications
CWE-787, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Feb 3, 2022CVE publishedPublication date reported by the CVE source.
  2. 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.

  1. 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

6.9NIST NVDAV:L/AC:M/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
7.5Insyde SoftwareCVSS:3.1/AV:L/AC:H/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.

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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
Privilegesadmin
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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