CVE-2021-27431
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 · uneditedARM CMSIS RTOS2 versions prior to 2.1.3 are vulnerable to integer wrap-around inosRtxMemoryAlloc (local malloc equivalent) function, which can lead to arbitrary memory allocation, resulting in unexpected behavior such as a crash or injected code execution.
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 confidenceARM CMSIS RTOS2 versions prior to 2.1.3 contain an integer wrap-around vulnerability in the osRtxMemoryAlloc function (the RTOS's memory allocation equivalent). This flaw allows an attacker to trigger arbitrary memory allocations through specially crafted requests that cause integer overflow, potentially leading to memory corruption, crashes, or arbitrary code execution.
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<= 2.1.3CVSS 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
- 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 CMSIS RTOS2 versionLocate the version header file in your CMSIS RTOS2 installation. Common paths include: CMSIS/OS/RTOS2/Include/os_version.h or similar version header files within the CMSIS pack. Open the file and find the version definition (often named __CMSIS_RTOS_VERSION or similar numeric version macro).Affected if The version number found is less than 2.1.3 (e.g., 2.1.2, 2.1.1, 2.1.0, or earlier)
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Verify dynamic memory allocation is enabledExamine your project configuration or source files for the RTOS memory pool settings. In CMSIS RTOS2, the memory allocation is controlled by the osRtxConfig.h or equivalent configuration header. Look for definitions such as osRtxMemoryAlloc or OS_LIB_MEM_DYNAMIC.Affected if Dynamic memory allocation is enabled (osRtxMemoryAlloc function is present and being used in the build)
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Check for osRtxMemoryAlloc usage in codebaseSearch your project source files for calls to osMemoryAlloc, osRtxMemoryAlloc, or related memory allocation functions from the RTOS. Also check if your project links against the CMSIS RTOS2 library that contains the vulnerable function.Affected if Your application code or linked libraries call osRtxMemoryAlloc or other CMSIS RTOS2 memory allocation functions
You are affected if your CMSIS RTOS2 version is 2.1.3 or earlier AND your project uses dynamic memory allocation through the osRtxMemoryAlloc function.
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 · scopedUpgrade to CMSIS RTOS2 version 2.1.3 or later which contains the fix for the integer wrap-around. If immediate patching is not feasible, implement严格的输入验证和边界检查 around memory allocation requests to mitigate exploitation.
CMSIS RTOS2 version 2.1.3
- 1. Identify all instances of ARM CMSIS RTOS2 in your project dependencies
- 2. Locate the CMSIS RTOS2 package configuration (typically in a package.json, CMSIS pack manifest, or build system configuration)
- 3. Update the CMSIS RTOS2 version specification to 2.1.3 or later
- 4. Rebuild the project to incorporate the updated library
- 5. Verify the build completes successfully and test the application to ensure proper RTOS functionality
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing12.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-27431 — 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-2021-27431 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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