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Insydeh2o Uefi BiosOperating system · Insyde

CVE-2020-5955

CRITICAL · 9.8 CVSS v3.1 Published 2021-11-03
Fix available
A fix is available. Upgrade to 05.04.21.0068 / 05.11.26.0015 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges 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 Int15MicrocodeSmm in Insyde InsydeH2O before 2021-10-14 on Intel client chipsets. A caller may be able to escalate privileges.

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

A privilege escalation vulnerability exists in the Int15MicrocodeSmm driver of InsydeH2O UEFI firmware (prior to 2021-10-14) on Intel client chipsets. The issue allows a caller to elevate privileges to System Management Mode (SMM), which operates at the highest privilege level on x86 processors, bypassing standard OS security boundaries.

MitigationUpdate the system BIOS/UEFI firmware to a version released after October 14, 2021 from the OEM or Insyde, as this is a firmware-level vulnerability that cannot be mitigated through configuration changes.

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
Insydeh2o Uefi BiosOperating system
Affected:< 05.32.30.0001< 05.41.35.0001< 05.42.11.0026< 05.04.21.0068< 05.42.09.0003< 05.21.51.0040< 05.34.09.0030< 05.32.47.0001< 05.23.45.0023< 05.21.43.0001< 05.23.04.0045< 05.11.26.0015

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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 the BIOS vendor
    Run `dmidecode -s bios-vendor` on Linux or `wmic bios get Manufacturer` on Windows to determine if the system uses InsydeH2O UEFI firmware
    Affected if The vendor is not Insyde or the string does not contain 'Insyde' - this CVE only affects InsydeH2O firmware
  2. Retrieve the installed BIOS version
    Run `dmidecode -s bios-version` on Linux or `wmic bios get SMBIOSBIOSVersion` on Windows to obtain the installed firmware version string
    Affected if A version string is returned - further version comparison is needed
  3. Map BIOS version to Insyde version numbers
    Consult the OEM release notes or Insyde documentation to map the installed BIOS version to the corresponding Insyde internal version numbers (e.g., 05.32.30.0001, 05.41.35.0001, etc.)
    Affected if The mapped Insyde version falls within the affected ranges listed in the CVE (< 05.32.30.0001, < 05.41.35.0001, < 05.42.11.0026, < 05.04.21.0068, < 05.42.09.0003, < 05.21.51.0040, < 05.34.09.0030, < 05.32.47.0001, < 05.23.45.0023, < 05.21.43.0001, < 05.23.04.0045, < 05.11.26.0015)
  4. Check firmware release date
    Run `dmidecode -s bios-release-date` or check the OEM/UEFI firmware update history to identify when the BIOS was released
    Affected if The firmware was released prior to October 14, 2021, as the patch was released on that date

The system is affected if it runs InsydeH2O UEFI firmware with an internal version number lower than any of the listed thresholds, or with a release date before October 14, 2021.

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 05.04.21.0068 / 05.11.26.0015 / 05.21.43.0001 or later
Fixed in 05.04.21.006805.11.26.001505.21.43.0001
Interim mitigation

Update the system BIOS/UEFI firmware to a version released after October 14, 2021 from the OEM or Insyde, as this is a firmware-level vulnerability that cannot be mitigated through configuration changes.

Recommended fix High confidence

InsydeH2O version >= 05.04.21.0068 (for 05.04 branch), >= 05.32.30.0001 (for 05.32 branch), >= 05.41.35.0001 (for 05.41 branch), or >= 05.42.11.0026 (for 05.42 branch), depending on your product line

  1. Check your system's current BIOS/UEFI version. This is typically found in the system setup (BIOS) or via system information tools.
  2. Identify your InsydeH2O BIOS version number. This is usually displayed on the BIOS setup main screen or can be retrieved via system utilities provided by your hardware manufacturer.
  3. Determine which version branch your current BIOS belongs to (05.04.x, 05.32.x, 05.41.x, or 05.42.x).
  4. Obtain the appropriate BIOS update from your original equipment manufacturer (OEM). The OEM integrates InsydeH2O into their firmware and provides the security updates. Common sources: Dell, HP, Lenovo, Acer, or other system vendors.
  5. Apply the BIOS update following the OEM's recommended procedure, which typically involves: downloading the update utility or BIOS file from the vendor's support site, running the update tool from within Windows or from a bootable USB, and ensuring the system has stable power during the update process.
  6. After updating, verify the new BIOS version matches or exceeds the fixed version for your branch (05.04.21.0068, 05.32.30.0001, 05.41.35.0001, or 05.42.11.0026).
Caveat BIOS updates carry inherent risk of system damage if interrupted; ensure stable power and follow OEM instructions precisely. Some OEM updates may reset BIOS settings to defaults.

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

Fix this in Insydeh2o Uefi Bios Scoped from the published advisory
  • Consultation8.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,940
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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-2020-5955 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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