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Insydeh2oApplication · Insyde

CVE-2023-27373

MEDIUM · 5.5 CVSS v3.1 Published 2023-08-07
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
57/100
Remediation priority · Elevated
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 Insyde InsydeH2O with kernel 5.0 through 5.5. Due to insufficient input validation, an attacker can tamper with a runtime-accessible EFI variable to cause a dynamic BAR setting to overlap SMRAM.

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

This is a firmware vulnerability in Insyde InsydeH2O UEFI firmware (kernel versions 5.0-5.5). Insufficient input validation on runtime-accessible EFI variables allows an attacker to manipulate dynamic Base Address Register (BAR) settings to overlap with System Management RAM (SMRAM). This could enable SMM (System Management Mode) code execution bypass or SMRAM contents exposure/exfiltration.

MitigationApply vendor-supplied firmware updates from Insyde that address input validation on EFI variables and BAR configuration. For systems unable to receive immediate updates, consider disabling unnecessary runtime EFI variable write access and monitor for unauthorized SMRAM access attempts.

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:= 5.0= 5.1= 5.2= 5.3= 5.4= 5.5

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

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

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 UEFI firmware vendor and version
    Use system information tools (such as `dmidecode -t bios` on Linux or system information utilities on Windows) to retrieve the BIOS/UEFI firmware vendor and version. Look for 'Insyde' or 'InsydeH2O' as the vendor.
    Affected if The firmware vendor is Insyde InsydeH2O and the version string contains 5.0, 5.1, 5.2, 5.3, 4, or 5.5 (kernel versions 5.0 through 5.5 are affected).
  2. Confirm runtime EFI variable write access is enabled
    On Linux systems, use `efivar -l` to list EFI variables and check for write access permissions, or use `efi-readvar` to examine variable attributes. On Windows, use `reg query HKLM\SYSTEM\CurrentControlSet\Services\Efivar` or similar tools to inspect EFI variable access settings.
    Affected if Runtime (post-boot) EFI variables are writable by software with sufficient privileges - the vulnerability requires writable EFI variables to manipulate BAR settings.
  3. Verify SMRAM is configured on the system
    Examine the system's memory map and PCI configuration space. On Linux, use `cat /proc/iomem` to view memory regions and check for SMRAM (System Management RAM) regions typically reserved in the 0xA0000-0xC0000 range or above 4GB. Use `lspci -v` to view PCI BAR assignments.
    Affected if The system has SMRAM regions allocated and PCI devices with configurable BAR settings - the vulnerability exploits BAR overlapping with SMRAM.
  4. Check for authorized SMRAM access tools or configurations
    Review system configurations and running software for tools that interact with SMM (System Management Mode) or SMRAM, such as SMM drivers or debugging tools. Use system auditing logs to identify any attempts to write to EFI variables related to BAR configuration.
    Affected if Unauthorized or unexpected attempts to modify EFI variables controlling BAR settings are detected, or unexpected SMRAM access patterns exist.

A system is affected if it runs Insyde InsydeH2O UEFI firmware with kernel versions 5.0 through 5.5 and has runtime-writable EFI variables with SMRAM configured, allowing potential BAR manipulation to overlap with SMRAM.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply vendor-supplied firmware updates from Insyde that address input validation on EFI variables and BAR configuration. For systems unable to receive immediate updates, consider disabling unnecessary runtime EFI variable write access and monitor for unauthorized SMRAM access attempts.

Fix this in Insydeh2o Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing12.0 h
  • Review / QA8.0 h
44.0 hours of engineering $7,720
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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-2023-27373 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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