CVE-2020-27631

Name: CVE-2020-27631
Creator: NVD / NIST
Published: 2023-10-10T17:15:10.453+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 1.08%

Last modified Jun 17, 2026

CVE-2020-27631 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. In Oryx CycloneTCP 1.9.6, TCP ISNs are improperly random.. EPSS estimates a 1.08% chance of exploitation in the next 30 days.

Description

In Oryx CycloneTCP 1.9.6, TCP ISNs are improperly random.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

1.08%

61.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-330

Affected Software

Vendor	Product	Versions
Oryx-Embedded	Cyclonetcp	1.9.6

References

https://www.cisa.gov/news-events/ics-advisories/icsa-21-042-01Third Party Advisory, US Government Resource
https://www.forescout.comThird Party Advisory
https://www.forescout.com/resources/numberjack-weak-isn-generation-in-embedded-tcpip-stacks/Third Party Advisory
https://www.cisa.gov/news-events/ics-advisories/icsa-21-042-01Third Party Advisory, US Government Resource
https://www.forescout.comThird Party Advisory
https://www.forescout.com/resources/numberjack-weak-isn-generation-in-embedded-tcpip-stacks/Third Party Advisory

Timeline

Published: Oct 10, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-27631?

In Oryx CycloneTCP 1.9.6, TCP ISNs are improperly random.

How severe is CVE-2020-27631?

CVE-2020-27631 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 1.08% probability of exploitation in the next 30 days.

How do I fix CVE-2020-27631?

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-2020-27631?

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

Scan your code now

Source: NVD / NIST