HOMEVULNERABILITIESCVE-2021-33627
HIGH

CVE-2021-33627

CWE-119Published: February 3, 2022· Updated: Jun 17, 2026

8.2
CVSS v3.1

Official Description

An issue was discovered in Insyde InsydeH2O Kernel 5.0 before 05.09.11, 5.1 before 05.17.11, 5.2 before 05.27.11, 5.3 before 05.36.11, 5.4 before 05.44.11, and 5.5 before 05.52.11 affecting FwBlockServiceSmm. Software SMI services that use the Communicate() function of the EFI_SMM_COMMUNICATION_PROTOCOL do not check whether the address of the buffer is valid, which allows use of SMRAM, MMIO, or OS kernel addresses.

NVD Source

Technical Analysis

CVE-2021-33627 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires high privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.2.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.

From a weakness classification perspective (CWE-119): Buffer overflow vulnerabilities can lead to arbitrary code execution or denial of service by corrupting adjacent memory.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorLocal
Attack ComplexityLow
Privileges Req.High
User InteractionNone
ScopeChanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Affected Vendors & Products

insyde1 product(s)
insydeh2o
siemens28 product(s)
simatic field pg m5 firmwaresimatic field pg m5simatic field pg m6 firmwaresimatic field pg m6simatic ipc127e firmwaresimatic ipc127esimatic ipc227g firmwaresimatic ipc227gsimatic ipc277g firmwaresimatic ipc277gsimatic ipc327g firmwaresimatic ipc327g+16
Source: NVD CPE · 29 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
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Official Patches & Advisories

All References (9)

Quick Facts

CVE IDCVE-2021-33627
CVSS Score8.2 / 10
SeverityHIGH
WeaknessCWE-119
CISA KEVNo
Affected2 vendor(s)
PublishedFeb 3, 2022

Related CVEs (CWE-119)

Recommended Actions

  • Apply vendor patches immediately
  • Monitor CVE-2021-33627 in threat intel feeds
  • Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.