CVE-2020-27339
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 · uneditedIn 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 AhciBusDxe, IdeBusDxe, NvmExpressDxe, SdHostDriverDxe, and SdMmcDeviceDxe drivers are 05.16.25, 05.26.25, 05.35.25, 05.43.25, and 05.51.25 (for Kernel 5.1 through 5.5).
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 · high confidenceSMM (System Management Mode) drivers in InsydeH2O kernel 5.x fail to properly validate CommBuffer and CommBufferSize parameters in the AhciBusDxe, IdeBusDxe, NvmExpressDxe, SdHostDriverDxe, and SdMmcDeviceDxe drivers. This allows attackers with SMM code execution to corrupt firmware or OS memory, potentially leading to persistent compromise or privilege escalation.
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>= 5.3, < 5.34.44>= 5.2, < 5.25.44>= 5.1, < 5.16.25>= 5.4, < 5.42.44>= 5.3, < 5.35.25>= 5.2, < 5.26.25>= 5.4, < 5.43.25all versionsall versionsall versionsall versionsall versionsall versionsall versionsCVSS 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
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:H/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 checksWork through these to decide whether this CVE applies to you.
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Identify InsydeH2O kernel versionUse system information tools, dmidecode, or firmware flashing utilities to retrieve the InsydeH2O kernel version installed on the systemAffected if Version falls within any of these ranges: >= 5.3 and < 5.34.44; >= 5.2 and < 5.25.44; >= 5.1 and < 5.16.25; >= 5.4 and < 5.42.44; >= 5.3 and < 5.35.25; >= 5.2 and < 5.26.25; or >= 5.4 and < 5.43.25
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Identify Siemens firmware versionCheck the firmware version on Siemens Ruggedcom Apr1808, Simatic Field Pg M5/M6, or Simatic Ipc devices using vendor-specific tools or device management interfacesAffected if Any version of the listed Siemens firmware products is installed (all versions are affected)
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Verify presence of affected SMM driversExtract and analyze the firmware image for the AhciBusDxe, IdeBusDxe, NvmExpressDxe, SdHostDriverDxe, or SdMmcDeviceDxe SMM drivers using firmware analysis toolsAffected if Any of these five drivers are present in the firmware SMM configuration
The system is affected if it runs an InsydeH2O kernel version within the vulnerable ranges OR uses any of the listed Siemens firmware products, AND contains the vulnerable SMM drivers (AhciBusDxe, IdeBusDxe, NvmExpressDxe, SdHostDriverDxe, or SdMmcDeviceDxe).
Generated from the published advisory. Verify against your own configuration.
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 data5.16.255.25.445.26.25
Update InsydeH2O firmware to the fixed versions (05.16.25, 05.26.25, 05.35.25, 05.43.25, or 05.51.25 depending on kernel version) for affected systems. Given the SMM attack surface, prioritize systems with direct physical access or exposed management interfaces.
- Consultation8.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-27339 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-27339 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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