How severe is CVE-2020-35684?

CVE-2020-35684 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2020-35684 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-35684?

CVE-2020-35684 primarily affects Hcc-embedded Nichestack. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-35684?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-35684 published?

CVE-2020-35684 was published on 2021-08-19 and last updated on 2026-06-17.

CVE-2020-35684

CVE-2020-35684 is a high-severity vulnerability in Hcc-embedded Nichestack with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 2% (81st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Hcc-embedded Nichestack
Published: 2021-08-19
Last modified: 2026-06-17

Description

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).

Frequently asked questions

What is CVE-2020-35684?: 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).
How severe is CVE-2020-35684?: CVE-2020-35684 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2020-35684 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-35684?: CVE-2020-35684 primarily affects Hcc-embedded Nichestack. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-35684?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2020-35684 published?: CVE-2020-35684 was published on 2021-08-19 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:hcc-embedded:nichestack:3.0:*:*:*:*:*:*:*
cpe:2.3:o:siemens:sentron_3wl_com35_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:sentron_3wa_com190_firmware:*:*:*:*:*:*:*:*

More vulnerabilities in Hcc-embedded Nichestack

CVE-2020-35685 — Critical (CVSS 9.1): An issue was discovered in HCC Nichestack 3.0. The code that generates Initial Sequence Numbers (ISNs) for TCP…
CVE-2021-36762 — High (CVSS 7.5): An issue was discovered in HCC Embedded InterNiche NicheStack through 4.3. The tfshnd():tftpsrv.c TFTP packet…
CVE-2021-31401 — High (CVSS 7.5): An issue was discovered in tcp_rcv() in nptcp.c in HCC embedded InterNiche 4.0.1. The TCP header processing code…
CVE-2021-27565 — High (CVSS 7.5): The web server in InterNiche NicheStack through 4.0.1 allows remote attackers to cause a denial of service (infinite…
CVE-2020-35683 — High (CVSS 7.5): An issue was discovered in HCC Nichestack 3.0. The code that parses ICMP packets relies on an unchecked value of the IP…
CVE-2021-31400 — High (CVSS 7.5): An issue was discovered in tcp_pulloutofband() in tcp_in.c in HCC embedded InterNiche 4.0.1. The TCP out-of-band…

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