CVE-2022-33906
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 · uneditedDMA transactions which are targeted at input buffers used for the FwBlockServiceSmm software SMI handler could cause SMRAM corruption through a TOCTOU attack. DMA transactions which are targeted at input buffers used for the software SMI handler used by the FwBlockServiceSmm driver could cause SMRAM corruption through a TOCTOU attack. This issue was discovered by Insyde engineering based on the general description provided by Intel's iSTARE group. Fixed in kernel 5.2: 05.27.23, 5.3: 05.36.23, 5.4: 05.44.23, 5.5: 05.52.23 https://www.insyde.com/security-pledge/SA-2022048
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 confidenceThis is a firmware-level vulnerability in Insyde UEFI implementations where DMA (Direct Memory Access) transactions targeted at input buffers used by the FwBlockServiceSmm driver's software SMI (System Management Interrupt) handler can cause SMRAM (System Management RAM) corruption through a TOCTOU (Time-of-Check-Time-of-Use) race condition. An attacker with DMA capability could exploit this to corrupt SMRAM, potentially executing code in the highest privilege System Management Mode.
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>= 5.2, < 5.2.05.27.23>= 5.3, < 5.3.05.36.23>= 5.4, < 5.4.05.44.23>= 5.5, < 5.5.05.52.23CVSS 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
- High
- Privileges
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:H/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 the UEFI firmware vendorUse system information tools (like dmidecode on Linux, or MSInfo32 on Windows) or check the BIOS/UEFI setup screen to determine if the firmware is from Insyde. Look for 'Insyde' or 'InsydeH2O' in the BIOS vendor or version strings.Affected if The firmware is not from Insyde (the vulnerability only affects Insyde UEFI implementations).
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Determine the installed Insyde Kernel versionCheck the UEFI firmware version string. On Windows, use 'wmic bios get smbiosbiosversion' or check in System Information. On Linux, check /sys/class/dmi/id/bios_version or use dmidecode -s bios-version. The version typically follows a format like '5.2.xx.xx' or similar indicating the Insyde Kernel version.Affected if The firmware version falls within these affected ranges: >= 5.2 and < 5.2.05.27.23; >= 5.3 and < 5.3.05.36.23; >= 5.4 and < 5.4.05.44.23; >= 5.5 and < 5.5.05.52.23.
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Locate the FwBlockServiceSmm driverExtract or dump the UEFI firmware (using tools like UEFITool, flashrom, or firmware extraction utilities) and search for the presence of the 'FwBlockServiceSmm' driver module within the firmware image.Affected if The vulnerable driver FwBlockServiceSmm is present in the firmware image (the driver contains the vulnerable code).
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Check DMA configuration in firmware settingsEnter the UEFI/BIOS setup (typically press Del, F2, or F12 during boot) and navigate to settings related to DMA, PCI Express, or I/O device configuration. Look for options like 'DMA', 'PCIe/PCI Bus Master', 'Above 4G Encoding', or similar DMA-enabling settings.Affected if DMA is enabled in the firmware settings (the vulnerability requires DMA transactions to reach the vulnerable input buffers).
A system is affected if it uses Insyde UEFI firmware with a Kernel version between the stated ranges AND contains the FwBlockServiceSmm driver AND has DMA enabled, allowing DMA transactions to target the vulnerable SMI handler buffers.
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.
dbcve · scoped5.2.05.27.235.3.05.36.235.4.05.44.23
Apply the vendor firmware updates (05.27.23 for kernel 5.2, 05.36.23 for kernel 5.3, 05.44.23 for kernel 5.4, 05.52.23 for kernel 5.5) from Insyde or the system OEM. If patching is not immediately feasible, consider disabling DMA or restricting DMA-capable devices in the firmware settings as a compensating control.
InsydeH2O kernel version 5.2.05.27.23 (or respective branch: 5.3.05.36.23, 5.4.05.44.23, or 5.5.05.52.23)
- 1. Identify the exact device/model and OEM that uses InsydeH2O kernel firmware (versions 5.2, 5.3, 5.4, or 5.5)
- 2. Contact the device OEM or visit their support website to obtain the latest UEFI/BIOS firmware update
- 3. Verify the firmware version matches or exceeds: 5.2.05.27.23, 5.3.05.36.23, 5.4.05.44.23, or 5.5.05.52.23 (depending on your kernel branch)
- 4. Follow OEM instructions to apply the firmware update (typically via BIOS flash utility or recovery process)
- 5. Confirm the vulnerability is resolved by checking the firmware version after update
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA6.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2022-33906 — 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-2022-33906 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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