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CVE Record

CVE-2020-35684: An issue was discovered in HCC Nichestack 3.0.

An 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).

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2020-35684 affects HCC NicheStack 3.0, a TCP/IP stack used in embedded systems. A malformed TCP/IP packet can cause memory to be read out of bounds during checksum handling, with a low-impact out-of-bounds write also noted. Business risk depends on which products include this stack and whether they are reachable over networks.

Executive priority

Treat this as an exposure-discovery item rather than a confirmed emergency. Prioritize environments with embedded or OT devices reachable from less trusted networks, because product mapping is incomplete and no active exploitation is cited.

Technical view

The TCP packet parser trusts the IP payload size from the IP header when calculating TCP payload length inside TCP checksum computation. If that value is smaller than the IP header size, the function may read outside expected memory bounds. The source bundle does not provide CVSS, CWE, fixed versions, or confirmed downstream affected products.

Likely exposure

Exposure is most likely in embedded, operational technology, or industrial devices that include HCC NicheStack 3.0 and process network TCP/IP traffic. The provided affected-product data is incomplete, so asset-specific vendor confirmation is required.

Exploitation context

The bundle does not cite active exploitation, and CISA KEV status is false. The issue is network-input driven, but the sources provided do not establish public exploit availability, weaponization, or practical impact beyond memory bounds violations.

Researcher notes

Key gaps are missing CVSS, CWE, fixed version, and confirmed downstream product list in the supplied CVE data. Analysis should focus on software bill of materials, vendor advisories, and controlled validation of packet-processing exposure without assuming exploitability beyond the described bounds issue.

Mitigation direction

  • Identify assets and firmware that use HCC NicheStack 3.0.
  • Check HCC, Siemens, CERT/CC, and device-vendor guidance for fixes or mitigations.
  • Limit network reachability to embedded or OT devices using this stack.
  • Prioritize segmentation for devices exposed to untrusted TCP/IP traffic.
  • Monitor for malformed IP/TCP traffic targeting sensitive embedded devices.

Validation and detection

  • Ask vendors whether deployed products include HCC NicheStack 3.0.
  • Compare device firmware against vendor advisories and support notices.
  • Review network paths to confirm affected devices are not broadly reachable.
  • Check monitoring for anomalous malformed IP/TCP packets.
  • Document uncertainty where product composition or firmware status is unknown.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2020-35684 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.