CVE-2021-33627

A vulnerability exists in SMM (System Management Mode) branch that registers a SWSMI handler that...

8.2 High

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.

Attack profile

How easy it is to exploit

Attack vector: Local
Complexity: Low
Privileges needed: High
User interaction: None

What an attacker can affect

Confidentiality: High
Integrity: High
Availability: High

Exploit likelihood

0.33%Down 0.4 points since Feb 3, 2022

What each source reports

NVD Score used 8.2

Record: CVE-2021-33627
CVSS 3.1: 8.2 HighCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
CVSS 2.0: 7.2 HighAV:L/AC:L/Au:N/C:C/I:C/A:C
Weakness: CWE-119
Updated: 2026-11-02

CVE List No score

Record: CVE-2021-33627
Updated: 2026-11-02

EUVDEUVD-2021-20304 No score

Record: EUVD-2021-20304
Updated: 2026-11-02

GitHub AdvisoriesGHSA-g6pg-5762-5mq6 8.2

A vulnerability exists in SMM (System Management Mode) branch that registers a SWSMI handler that...

A vulnerability exists in SMM (System Management Mode) branch that registers a SWSMI handler that does not sufficiently check or validate the allocated buffer pointer(CommBuffer). This can be used by an attacker to corrupt data in SMRAM memory and even lead to arbitrary code execution.

Record: GHSA-g6pg-5762-5mq6
CVSS 3.1: 8.2 HighCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
Weakness: CWE-119
Updated: 2026-11-02

Affected products

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History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-33627 is a high vulnerability (CVSS 8.2) in Insyde Insydeh2o, published February 3, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.33%, the 26th percentile. No source names a fixed version.