CVE-2020-35684
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 Nichestack 3.0. The code that parses TCP packets relies on an unchecked value of the IP payload size (extracted from the IP header) to compute the length of the TCP payload within the TCP checksum computation function. When the IP payload size is set to be smaller than the size of the IP header, the TCP checksum computation function may read out of bounds (a low-impact write-out-of-bounds is also possible).
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 confidenceHCC Nichestack 3.0 contains an out-of-bounds read vulnerability in its TCP checksum computation function. The function uses the IP payload size from the IP header without validating that it is larger than the IP header size, allowing malformed packets to trigger memory access beyond buffer boundaries during TCP checksum calculation.
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= 3.0< 1.2.0< 2.0.0CVSS 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 device runs HCC NichestackReview your product documentation, software bill of materials, or firmware image for references to 'HCC Embedded' or 'Nichestack' TCP/IP stackAffected if Your device uses HCC Nichestack version 3.0
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Determine the exact Nichestack versionCheck firmware metadata, library version strings, or contact HCC Embedded for version confirmation. For Siemens devices, check the firmware version displayed in the web UI or via SNMPAffected if Version is exactly 3.0 (for HCC) or versions are below 1.2.0 for Sentron 3wl Com35 or below 2.0.0 for Sentron 3wa Com190
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Confirm TCP/IP processing is enabledVerify that the device has network interfaces configured and TCP/IP stack is active. Check if the device listens on any TCP ports or handles network trafficAffected if The device processes network traffic (this is the attack surface for the vulnerability)
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Inspect IP header handling in network logsCapture network traffic using a packet sniffer and examine packets sent to the device. Look for any malformed packets with IP header length inconsistenciesAffected if The device accepts and processes packets without additional validation on IP header length fields
You are affected if your device runs HCC Nichestack 3.0 (or Siemens Sentron 3wl Com35 below 1.2.0 / 3wa Com190 below 2.0.0) and processes network traffic, as the vulnerability triggers when malformed packets with inconsistent IP header length are received.
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 · scoped1.2.02.0.0
Update to a patched version of HCC Nichestack if available; otherwise, add validation to ensure IP payload size exceeds IP header size before using it in TCP checksum computation, and implement network-level filtering to drop packets with inconsistent IP header length fields.
Sentron 3wl Com35: firmware >= 1.2.0 | Sentron 3wa Com190: firmware >= 2.0.0 | HCC Nichestack: contact vendor for patched release
- Identify all devices running Nichestack 3.0 or Siemens Sentron 3wl Com35 (firmware < 1.2.0) or Sentron 3wa Com190 (firmware < 2.0.0)
- Consult Siemens cert-portal.siemens.com for the latest security updates for these products
- For Sentron 3wl Com35 devices: upgrade firmware to version 1.2.0 or later
- For Sentron 3wa Com190 devices: upgrade firmware to version 2.0.0 or later
- If using Nichestack 3.0 directly in other products, contact HCC Embedded (www.hcc-embedded.com) for the patched Nichestack version
- Verify the upgrade was successful by checking firmware version and running vulnerability scans
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-2020-35684 — 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-2020-35684 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
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- Version or environment caveats, and links to real fixes
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