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CVE-2020-35685
An issue was discovered in HCC Nichestack 3.0. The code that generates Initial Sequence Numbers (ISNs) for TCP connections derives the ISN…
Critical9.1EPSS 2.1%
- Published
- Updated
- Reserved
- Assigned by
- mitre
Description
An issue was discovered in HCC Nichestack 3.0. The code that generates Initial Sequence Numbers (ISNs) for TCP connections derives the ISN from an insufficiently random source. As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existing ones or spoof future ones. (Proper ISN generation should aim to follow at least the specifications outlined in RFC 6528.)
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | Critical9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
- EPSS (exploitation in 30 days)
- 2.1% · top 19% of all CVEs (6 Nov 2026)
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The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.1.
Weakness
Affected products
n/a
- affected n/a
References (4)
- https://www.hcc-embedded.com (opens in a new tab)x_refsource_MISCx_transferred
- https://cert-portal.siemens.com/productcert/pdf/ssa-789208.pdf (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://www.forescout.com/blog/new-critical-operational-technology-vulnerabilities-found-on-nichestack/ (opens in a new tab)x_refsource_MISCx_transferred
- VU#608209 (opens in a new tab)third-party-advisoryx_refsource_CERT-VNx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2020-35685)Record last updated .