CVE-2021-31401Network attack vector

Application-dependent failure via unchecked IP packet length

Published Aug 19, 2021 · Updated Aug 3, 2024

Integer overflow in tcp_rcv() in HCC Embedded InterNiche before 4.3 allows remote attackers to trigger application-dependent failure. tcp_rcv() subtracts the TCP header length from an unchecked IP total-length field, allowing the computed IP data length to wrap. No authentication or user interaction is required, but the resulting effect depends on the embedding application and device implementation.

CVSS severity7.5
High
EPSS probability2.25%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in tcp_rcv() in HCC Embedded InterNiche before 4.3 allows remote attackers to trigger application-dependent failure. tcp_rcv() subtracts the TCP header length from an unchecked IP total-length field, allowing the computed IP data length to wrap. No authentication or user interaction is required, but the resulting effect depends on the embedding application and device implementation.

The record

CVE
CVE-2021-31401
Published
Aug 19, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-20, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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