CVE-2020-35684

Name: CVE-2020-35684
Creator: NVD / NIST
Published: 2021-08-19T12:15:08.02+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 2.29%

Last modified Jun 17, 2026

CVE-2020-35684 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 2.29% chance of exploitation in the next 30 days.

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).

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

2.29%

81.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-20

Affected Software

Vendor	Product	Versions
Hcc-Embedded	Nichestack	3.0
Siemens	Sentron 3wl Com35 Firmware	< 1.2.0
Siemens	Sentron 3wa Com190 Firmware	< 2.0.0

References

https://cert-portal.siemens.com/productcert/pdf/ssa-789208.pdfMitigation, Third Party Advisory
https://www.forescout.com/blog/new-critical-operational-technology-vulnerabilities-found-on-nichestack/Mitigation, Third Party Advisory
https://www.hcc-embedded.comProduct
https://www.kb.cert.org/vuls/id/608209Third Party Advisory, US Government Resource
https://cert-portal.siemens.com/productcert/pdf/ssa-789208.pdfMitigation, Third Party Advisory
https://www.forescout.com/blog/new-critical-operational-technology-vulnerabilities-found-on-nichestack/Mitigation, Third Party Advisory
https://www.hcc-embedded.comProduct
https://www.kb.cert.org/vuls/id/608209Third Party Advisory, US Government Resource

Timeline

Published: Aug 19, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-35684?

How severe is CVE-2020-35684?

CVE-2020-35684 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 2.29% probability of exploitation in the next 30 days.

How do I fix CVE-2020-35684?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-35684?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST