CVE-2021-43997
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 · uneditedFreeRTOS versions 10.2.0 through 10.4.5 do not prevent non-kernel code from calling the xPortRaisePrivilege internal function to raise privilege. FreeRTOS versions through 10.4.6 do not prevent a third party that has already independently gained the ability to execute injected code to achieve further privilege escalation by branching directly inside a FreeRTOS MPU API wrapper function with a manually crafted stack frame. These issues affect ARMv7-M MPU ports, and ARMv8-M ports with MPU support enabled (i.e. configENABLE_MPU set to 1). These are fixed in V10.5.0 and in V10.4.3-LTS Patch 3.
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 confidenceFreeRTOS versions 10.2.0-10.4.5 fail to prevent non-kernel code from calling the internal xPortRaisePrivilege function to elevate privileges. Additionally, versions through 10.4.6 allow privilege escalation by branching inside MPU API wrapper functions with crafted stack frames. These flaws affect ARMv7-M MPU ports and ARMv8-M ports with configENABLE_MPU set to 1.
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>= 10.2.0, < 10.4.6= 10.4.3CVSS 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
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/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 FreeRTOS version in useLocate the FreeRTOS version definition in your codebase (typically in FreeRTOS.h or a version header file) and note the major.minor.patch numbersAffected if The version is 10.2.0 through 10.4.5 inclusive, or exactly 10.4.3, or 10.4.6
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Determine the target CPU architectureCheck the processor architecture being used - look for ARM Cortex-M series defines or compiler settings that specify the ARM architecture variantAffected if The target is ARMv7-M or ARMv8-M architecture
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Verify MPU support is enabledLocate the FreeRTOSConfig.h file and check if the macro configENABLE_MPU is defined and set to 1Affected if configENABLE_MPU is defined and equals 1
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Confirm use of MPU port filesIdentify which FreeRTOS port files are being used - MPU-specific ports are typically located in a subdirectory containing 'MPU' in the path (e.g., ARM_CM7_MPU/rvpt)Affected if The build uses MPU-specific port files for ARMv7-M or ARMv8-M
You are affected if your FreeRTOS version falls between 10.2.0-10.4.6, your target is ARMv7-M or ARMv8-M, and configENABLE_MPU is set to 1 enabling the MPU port.
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 · scoped10.4.6
Upgrade FreeRTOS to V10.5.0 or V10.4.3-LTS Patch 3 to obtain the fixed MPU wrapper functions and protected xPortRaisePrivilege access.
FreeRTOS V10.5.0 or FreeRTOS V10.4.3-LTS Patch 3
- 1. Identify the current FreeRTOS version in use by checking the version header file (typically FreeRTOS.h or version.h)
- 2. If using FreeRTOS 10.2.0 through 10.4.5 (non-LTS), upgrade to FreeRTOS V10.5.0 or later
- 3. If using FreeRTOS 10.4.3 LTS, apply FreeRTOS V10.4.3-LTS Patch 3
- 4. After upgrade, verify the ARMv7-M MPU or ARMv8-M MPU configurations are still correctly set for your hardware platform
- 5. Rebuild and test the firmware to ensure functionality is preserved
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-43997 — 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-2021-43997 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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