CVE-2020-27634

Name: CVE-2020-27634
Creator: NVD / NIST
Published: 2023-10-10T17:15:10.657+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.1/10EPSS 1.72%

Last modified Jun 17, 2026

CVE-2020-27634 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. In Contiki 4.5, TCP ISNs are improperly random.. EPSS estimates a 1.72% chance of exploitation in the next 30 days.

Description

In Contiki 4.5, TCP ISNs are improperly random.

Metrics

CVSS 3.1

9.1/10

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

EPSS Probability

1.72%

74.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-330

Affected Software

Vendor	Product	Versions
Contiki-Ng	Contiki-Ng	4.5

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-2020-27634?

In Contiki 4.5, TCP ISNs are improperly random.

How severe is CVE-2020-27634?

CVE-2020-27634 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 1.72% probability of exploitation in the next 30 days.

How do I fix CVE-2020-27634?

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-2020-27634?

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

Scan your code now

Source: NVD / NIST