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CVE Record

CVE-2021-31401: An issue was discovered in tcp_rcv() in nptcp.c in HCC embedded InterNiche 4.0.1.

An issue was discovered in tcp_rcv() in nptcp.c in HCC embedded InterNiche 4.0.1. The TCP header processing code doesn't sanitize the value of the IP total length field (header length + data length). With a crafted IP packet, an integer overflow occurs whenever the value of the IP data length is calculated by subtracting the length of the header from the total length of the IP packet.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-31401 is a TCP packet-handling flaw in HCC embedded InterNiche 4.0.1. A specially crafted IP packet can trigger an integer overflow while the stack calculates TCP payload length. The public bundle does not provide a CVSS score, confirmed affected device list, or confirmed exploitation evidence.

Executive priority

Treat this as an exposure-discovery priority, especially in OT or embedded networks. Urgency depends on whether vulnerable devices are deployed and reachable. The public evidence does not justify claiming active exploitation or a confirmed universal patch path.

Technical view

The flaw is in tcp_rcv() in nptcp.c. The code does not sanitize the IP total length value before subtracting the header length to calculate IP data length, allowing integer overflow with crafted IP packets. Impact is not fully stated in the provided sources.

Likely exposure

Exposure is most likely in embedded or operational technology devices that include HCC embedded InterNiche 4.0.1. The CVE record lists affected vendor and product as n/a, so product-level exposure must be confirmed through vendor advisories, SBOMs, firmware records, or supplier statements.

Exploitation context

The source bundle supports crafted-packet reachability but does not show active exploitation. The CVE is not marked as CISA KEV in the provided data. Any reachable TCP/IP stack in embedded environments should still be reviewed because vulnerable networking code may sit below application controls.

Researcher notes

The strongest confirmed detail is the integer overflow condition in TCP header processing. The bundle lacks CVSS, CWE, affected CPEs, exploit status, and precise impact. Avoid product assumptions beyond HCC embedded InterNiche 4.0.1 unless validated by a device-specific advisory.

Mitigation direction

  • Identify devices or firmware using HCC embedded InterNiche 4.0.1.
  • Review Siemens, CERT/CC, HCC, and device-vendor guidance for fixes.
  • Restrict network exposure to affected embedded devices where possible.
  • Apply vendor-approved firmware updates or mitigations when available.
  • Monitor for malformed IP/TCP traffic targeting exposed embedded systems.

Validation and detection

  • Search SBOMs and firmware inventories for InterNiche 4.0.1.
  • Check vendor advisories for each exposed device model.
  • Confirm whether affected devices receive unsolicited IP/TCP traffic.
  • Review network segmentation around OT and embedded assets.
  • Document unresolved vendor confirmation gaps for risk acceptance.
Prepared
Confidence
medium
Sources
5

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-2021-31401 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
4Source 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.