CVE-2021-41842
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 · uneditedAn issue was discovered in AtaLegacySmm in the kernel 5.0 before 05.08.46, 5.1 before 05.16.46, 5.2 before 05.26.46, 5.3 before 05.35.46, 5.4 before 05.43.46, and 5.5 before 05.51.45 in Insyde InsydeH2O. Code execution can occur because the SMI handler lacks a CommBuffer 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 confidenceA vulnerability exists in the AtaLegacySmm SMI (System Management Interrupt) handler in InsydeH2O UEFI firmware across multiple kernel 5.x versions. The SMI handler lacks a CommBuffer (Communication Buffer) validation check, allowing an attacker to achieve arbitrary code execution in SMM (System Management Mode) with the highest privilege level on the system.
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>= 5.0, < 05.08.46>= 5.1, < 05.16.46>= 5.2, < 05.26.46>= 5.3, < 05.35.46> 5.4, < 05.43.46>= 5.5, < 05.51.45CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Identify InsydeH2O firmware versionAccess UEFI setup (press Del/F2 during boot) and check the firmware version under the 'Main' or 'Information' tab, or use 'dmidecode -s bios-version' if available. The version format is typically 05.xx.xx.Affected if The installed version falls within any of these ranges: >= 5.0 and < 05.08.46; >= 5.1 and < 05.16.46; >= 5.2 and < 05.26.46; >= 5.3 and < 05.35.46; > 5.4 and < 05.43.46; >= 5.5 and < 05.51.45.
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Verify if ATA legacy mode is enabledEnter UEFI setup and navigate to 'Advanced' or 'Storage' settings. Look for options such as 'ATA Legacy Mode', 'Legacy USB', 'Legacy ROM Support', or 'IDE/AHCI Mode' configuration. Check whether legacy ATA/IDE support is turned on.Affected if ATA legacy mode, legacy ATA support, or IDE compatibility mode is enabled in the firmware settings.
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Confirm AtaLegacySmm module presenceExamine the UEFI firmware image (if obtainable via firmware update tools or extracting the ROM) for the presence of the AtaLegacySmm driver module. This is typically found in the SMM driver volume.Affected if The AtaLegacySmm driver is present in the firmware and ATA legacy mode is enabled, creating the attack surface.
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Check for SMM protection mechanismsReview UEFI settings for SMM-related protections such as 'SMM Protection', 'SMM Security' or 'Intel Boot Guard' status. Alternatively, use OS-level tools like 'chipsec' (if available) to query SMM configuration.Affected if No SMM protection or CommBuffer validation is configured, and the firmware version is in the affected range.
A system is affected if it runs InsydeH2O firmware version within the specified ranges AND has ATA legacy mode enabled in the UEFI settings, allowing the vulnerable AtaLegacySmm SMI handler to be exploitable.
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 · scoped05.08.4605.16.4605.26.46
Apply the vendor-supplied firmware update from Insyde for affected systems. If no update is available, consider disabling ATA legacy mode in firmware settings or implementing additional runtime protection mechanisms to detect SMM deviations.
InsydeH2O kernel 5.0: 05.08.46 or later; kernel 5.1: 05.16.46 or later; kernel 5.2: 05.26.46 or later; kernel 5.3: 05.35.46 or later; kernel 5.4: 05.43.46 or later; kernel 5.5: 05.51.45 or later
- 1. Identify the current InsydeH2O firmware version installed on the affected system by accessing the UEFI/BIOS setup utility (typically accessed by pressing Del, F2, or F12 during boot)
- 2. Check the kernel version displayed in the UEFI/BIOS information screen (typically shows as 5.0, 5.1, 5.2, 5.3, etc.)
- 3. Download the updated InsydeH2O firmware from the system manufacturer's support website - contact the OEM (Original Equipment Manufacturer) for the specific BIOS/UEFI update containing the Insyde fix
- 4. Apply the firmware update using the OEM's recommended method (e.g., BIOS flash utility, Windows update, or bootable USB)
- 5. Verify the firmware was successfully updated to a version at or above: 05.08.46 for kernel 5.0, 05.16.46 for kernel 5.1, 05.26.46 for kernel 5.2, 05.35.46 for kernel 5.3, 05.43.46 for kernel 5.4, or 05.51.45 for kernel 5.5
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation8.0 h
- Implementation16.0 h
- Testing8.0 h
- Review / QA4.0 h
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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 sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-41842 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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