Cyber Resilience

CVE-2020-35685

Critical

Published: 19 August 2021

Published
19 August 2021
Modified
21 November 2024
KEV Added
Patch
CVSS Score v3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS Score 0.0041 61.6th percentile
Risk Priority 18 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2020-35685 is a critical-severity Use of Insufficiently Random Values (CWE-330) vulnerability in Hcc-Embedded Nichestack. Its CVSS base score is 9.1 (Critical).

Operationally, ranked in the top 38.4% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

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…

more

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.)

CWE(s)

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

hcc-embedded
nichestack
3.0
siemens
sentron 3wa com190 firmware
≤ 2.0.0
siemens
sentron 3wl com35 firmware
≤ 1.2.0

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-330

Key generation under controlled management uses approved random-bit sources rather than insufficiently random values.

References