CVE-2021-33834

An issue was discovered in iscflashx64.sys 3.9.3.0 in Insyde H2OFFT 6.20.00. When handling IOCTL 0x22229a, the input used to allocate a buffer and copy memory is mishandled. This could cause memory corruption or a system crash.

Published: 2023-09-07 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-33834 is rated Low Risk (31.5/100): CVSS High severity, with low exploitation likelihood (EPSS 0.19%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-33834

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.06% 0.19% +0.12%
2 2025-03-17 0.04% 0.06% +0.02%
3 2023-09-08 — 0.04% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-33834

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.1 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.2 [email protected]

Weakness enumeration for CVE-2021-33834

Affected software / configurations for CVE-2021-33834

Vendor Product Version Raw CPE
insyde h2offt 6.20.00 cpe:2.3:a:insyde:h2offt:6.20.00:*:*:*:*:*:*:*
insyde iscflashx64.sys 3.9.3.0 cpe:2.3:a:insyde:iscflashx64.sys:3.9.3.0:*:*:*:*:*:*:*

References for CVE-2021-33834

cvelogic Threat Intelligence