CVE-2021-33626

In the kernel in Insyde InsydeH2O 5.x, certain SMM drivers did not correctly validate the...

7.8 High

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(QWORD values for CommBuffer). This can be used by an attacker to corrupt data in SMRAM memory and even lead to arbitrary code execution.

Attack profile

How easy it is to exploit

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

What an attacker can affect

Confidentiality: High
Integrity: High
Availability: High

Exploit likelihood

0.31%Down 0.1 points since Oct 1, 2021

What each source reports

NVD Score used 7.8

Record: CVE-2021-33626
CVSS 3.1: 7.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS 2.0: 4.6 MediumAV:L/AC:L/Au:N/C:P/I:P/A:P
Weakness: CWE-829
Updated: 2026-11-02

CVE List No score

Record: CVE-2021-33626
Updated: 2026-11-02

EUVDEUVD-2021-20303 No score

Record: EUVD-2021-20303
Updated: 2026-11-02

GitHub AdvisoriesGHSA-9g63-gv45-4242 7.8

In the kernel in Insyde InsydeH2O 5.x, certain SMM drivers did not correctly validate the...

In the kernel in Insyde InsydeH2O 5.x, certain SMM drivers did not correctly validate the CommBuffer and CommBufferSize parameters, allowing callers to corrupt either the firmware or the OS memory. The fixed versions for this issue in the PnpSmm, SmmResourceCheckDxe, and BeepStatusCode drivers are 05.08.23, 05.16.23, 05.26.23, 05.35.23, 05.43.23, and 05.51.23 (for Kernel 5.0 through 5.5).

Record: GHSA-9g63-gv45-4242
CVSS 3.1: 7.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness: CWE-829
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-2021-33626 is a high vulnerability (CVSS 7.8) in Insyde Insydeh2o, published October 1, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.31%, the 23rd percentile. No source names a fixed version.