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Insydeh2oApplication · Insyde

CVE-2021-41838

HIGH · 8.2 CVSS v3.1 Published 2022-02-03
Fix available
A fix is available. Upgrade to 5.16.42 / 5.26.42 or later.
See remediation →
84/100
Remediation priority · High
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An issue was discovered in SdHostDriver in the kernel 5.0 through 5.5 in Insyde InsydeH2O. There is an SMM callout that allows an attacker to access the System Management Mode and execute arbitrary code. This occurs because of a Numeric Range Comparison Without a Minimum Check.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

The SdHostDriver in InsydeH2O firmware contains an SMM callout vulnerability stemming from a numeric range comparison missing a minimum check. This allows an authenticated attacker to bypass SMM security boundaries and execute arbitrary code in the System Management Mode, a highly privileged CPU mode operating below the operating system.

MitigationApply vendor-supplied firmware patches for InsydeH2O that address the SMM callout in SdHostDriver. If no patch is available, consider disabling the SD host driver or implementing additional system hardening to limit SMM exposure.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Insydeh2oApplication
Affected:>= 5.1, < 5.16.42>= 5.2, < 5.26.42>= 5.3, < 5.35.42>= 5.4, < 5.43.42>= 5.5, < 5.51.42
Simatic Field Pg M5 FirmwareOperating system
Affected:all versions
Simatic Field Pg M6 FirmwareOperating system
Affected:all versions
Simatic Ipc127e FirmwareOperating system
Affected:all versions
Simatic Ipc227g FirmwareOperating system
Affected:all versions
Simatic Ipc277g FirmwareOperating system
Affected:all versions
Simatic Ipc327g FirmwareOperating system
Affected:all versions
Simatic Ipc377g FirmwareOperating system
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
High
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify firmware vendor and version
    Access system BIOS/UEFI setup (typically press Del/F2 during boot) and locate the BIOS version information, or use commands like 'dmidecode -s bios-version' (Linux) or 'wmic bios get smbiosbiosversion' (Windows)
    Affected if The firmware is identified as InsydeH2O with a version that falls within the affected ranges (>=5.1/<5.16.42, >=5.2/<5.26.42, >=5.3/<5.35.42, >=5.4/<5.43.42, or >=5.5/<5.51.42)
  2. Confirm system is an affected Siemens model
    Check system model information via BIOS, system label, or commands like 'dmidecode -s system-product-name' (Linux) or 'wmic computersystem get model' (Windows)
    Affected if The system is a Siemens Simatic Field Pg M5, M6, Simatic IPC127e, IPC227g, IPC277g, IPC327g, or IPC377g (all versions of these models are affected)
  3. Verify SdHostDriver presence in firmware
    Inspect firmware image or use UEFI shell tools to enumerate drivers; check firmware update packages for the presence of SdHostDriver driver
    Affected if The SdHostDriver is present in the firmware (this driver is required for the vulnerability to be exploitable)
  4. Check if SD host controller is enabled
    Examine BIOS settings for SD host controller/enable SD card slot options, or inspect UEFI variable settings related to SdHostDriver configuration
    Affected if The SD host controller is enabled in the firmware configuration

You are affected if your system uses InsydeH2O firmware within the specified version ranges or is any version of the listed Siemens industrial devices, and the SdHostDriver is present and the SD host controller is enabled.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.16.42 / 5.26.42 / 5.35.42 or later
Fixed in 5.16.425.26.425.35.42
Interim mitigation

Apply vendor-supplied firmware patches for InsydeH2O that address the SMM callout in SdHostDriver. If no patch is available, consider disabling the SD host driver or implementing additional system hardening to limit SMM exposure.

Recommended fix Moderate confidence

InsydeH2O version 5.16.42, 5.26.42, 5.35.42, or 5.43.42 (depending on which branch the current firmware is on)

  1. Identify the exact InsydeH2O firmware version currently installed on the affected device
  2. Based on the current version branch, upgrade to the corresponding fixed version: 5.16.42 (for 5.1.x), 5.26.42 (for 5.2.x), 5.35.42 (for 5.3.x), or 5.43.42 (for 5.4.x)
  3. Obtain the updated firmware from the device manufacturer (Insyde or Siemens depending on the product)
  4. Apply the firmware update following the manufacturer's standard firmware update procedure
  5. For Siemens Simatic devices (Field PG M5/M6, IPC127e, IPC227g, IPC277g, IPC327g, IPC377g), contact Siemens for specific firmware updates as these are listed as 'all versions' affected
  6. Verify the update was successful by checking the firmware version after flashing
Caveat Firmware updates carry risk of bricking the device if interrupted; ensure stable power and follow manufacturer update procedures exactly

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Insydeh2o Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
30.0 hours of engineering $5,280
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-41838 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data