CVE-2021-43997

CVE-2021-43997 is a high-severity vulnerability in Amazon Freertos with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Description

FreeRTOS 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.

Frequently asked questions

What is CVE-2021-43997?
FreeRTOS 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.
How severe is CVE-2021-43997?
CVE-2021-43997 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-43997 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (23rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43997?
CVE-2021-43997 primarily affects Amazon Freertos. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-43997?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-43997 published?
CVE-2021-43997 was published on 2021-11-17 and last updated on 2026-06-17.

References

Affected products (2)

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