PT-2021-2230 · Fnet · Fnet

Amine Amri + 3 · Published 2021-03-05 · Updated 2023-10-13 · CVE-2020-27633

Positive Technologies (AI Summary)

CVSS v3.1

9.1

Critical

Base vector

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

Name of the Vulnerable Software and Affected Versions FNET version 4.6.3

Description The issue is related to the improper randomness of TCP Initial Sequence Numbers (ISNs) in the FNET protocol stack implementation. This could allow a remote attacker to gain unauthorized access to protected information. The problem stems from the use of insufficiently random values.

Recommendations For FNET version 4.6.3, consider implementing additional randomness measures for TCP ISNs to mitigate the risk of exploitation. As a temporary workaround, restrict access to sensitive information until a patch is available. At the moment, there is no information about a newer version that contains a fix for this vulnerability.

Use of Insufficiently Random Values

Weakness Enumeration

CWE-330

Related Identifiers

BDU:2021-01175

CVE-2020-27633

Affected Products

Fnet

References · 13

• https://osv.dev/vulnerability/CVE-2020-27633 · Vendor Advisory
• https://bdu.fstec.ru/vul/2021-01175 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2020-27633 · Security Note
• https://fnet.sourceforge.io · Note
• https://cisa.gov/news-events/ics-advisories/icsa-21-042-01 · Note
• https://forescout.com/company/blog/numberjack-forescout-research-labs-finds-nine-isn-generation-vulnerabilities-affecting-tcpip-stacks · Note
• https://securitylab.ru/vulnerability/516448.php · Note
• https://t.me/cibsecurity/71966 · Telegram Post
• https://forescout.com/resources/numberjack-weak-isn-generation-in-embedded-tcpip-stacks · Note
• https://cybersecurity-help.cz/vdb/SB2021021016 · Note
• https://t.me/cvenotify/59183 · Telegram Post
• https://forescout.com · Note
• https://securitylab.ru/news/516461.php · Note