CVE-2021-31227
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 HCC embedded InterNiche 4.0.1. A potential heap buffer overflow exists in the code that parses the HTTP POST request, due to an incorrect signed integer comparison. This vulnerability requires the attacker to send a malformed HTTP packet with a negative Content-Length, which bypasses the size checks and results in a large heap overflow in the wbs_multidata buffer copy.
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 confidenceHeap buffer overflow vulnerability in HCC embedded InterNiche 4.0.1 HTTP POST request parser. An incorrect signed integer comparison allows a negative Content-Length value to bypass size checks, enabling a large heap overflow when data is copied into the wbs_multidata buffer.
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< 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
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 if your product uses HCC Embedded NichestackCheck product documentation, software bill of materials (SBOM), or source code dependencies for references to 'InterNiche', 'Nichestack', or 'HCC Embedded'. Search for 'niche.h' or similar InterNiche header files in your codebase.Affected if Your product bundles or uses HCC Embedded Nichestack as its TCP/IP/HTTP stack.
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Determine the installed InterNiche versionSearch for version strings in compiled binaries or libraries (e.g., strings binary | grep -i 'Niche' or check version fields in NicheStack-related DLLs/SOs). Inspect any 'version.h' or 'niche_version.h' files included in the firmware/software.Affected if The version is lower than 4.3 (e.g., 4.0.1, 4.1, 4.2.x).
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Confirm HTTP server module is enabledInspect the application configuration (config.h, net_config.c, or similar) for enabled HTTP server definitions such as ENABLE_HTTP_SERVER, NCH_HTTP, or HTTP_SERVER defined as 1. Check if the HTTP server daemon task is started in main initialization code.Affected if HTTP server functionality is compiled into the firmware and actively running.
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Verify POST request handling is activeCheck if your application exposes any HTTP endpoints that accept POST methods. Review the web server configuration for form handlers, API endpoints, or file upload handlers. Look for references to 'wbs_multidata' or 'Content-Length' handling in the code.Affected if The HTTP server accepts or processes POST requests, which triggers Content-Length header parsing.
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Inspect for Content-Length validationSearch the codebase for Content-Length header processing logic. Look for the comparison operation that handles Content-Length values (typically in http.c, httpd.c, or nhttp.c). Check if there is a signed vs unsigned integer check or explicit validation rejecting negative values.Affected if The code lacks validation to reject negative Content-Length values, allowing them to bypass size checks.
Your environment is affected if it uses HCC Embedded Nichestack version below 4.3 with the HTTP server enabled and POST request handling active, allowing negative Content-Length values to trigger the heap overflow.
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 · scoped4.3
Apply any available vendor patch for InterNiche 4.0.1; if no patch exists, implement input validation at network boundaries to reject HTTP requests with negative Content-Length headers and restrict network access to the affected service.
Nichestack 4.3
- 1. Identify all deployed instances of HCC embedded InterNache (Nichestack) in your environment
- 2. Verify the currently installed version of Nichestack in each deployment
- 3. For deployments running Nichestack versions prior to 4.3, obtain the updated version 4.3 or later from HCC (Hillcrest Consulting Associates)
- 4. Test the new Nichestack version in a staging environment to verify compatibility with your application
- 5. Deploy the upgraded Nichestack version to production systems following your standard change management process
- 6. Verify that HTTP POST request handling functions correctly after the upgrade
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-31227 — 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-2021-31227 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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