CVE-2021-38311

Name: CVE-2021-38311
Creator: NVD / NIST
Published: 2021-08-09T22:15:08.733+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 0.94%

Last modified Jun 17, 2026

CVE-2021-38311 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. In Contiki 3.0, potential nonterminating acknowledgment loops exist in the Telnet service. When the negotiated options are already disabled, servers still respond to DONT and WONT requests with WONT or DONT commands, which may lead to infinite acknowledgment loops, denial of service, and excessive CPU consumption.. EPSS estimates a 0.94% chance of exploitation in the next 30 days.

Description

In Contiki 3.0, potential nonterminating acknowledgment loops exist in the Telnet service. When the negotiated options are already disabled, servers still respond to DONT and WONT requests with WONT or DONT commands, which may lead to infinite acknowledgment loops, denial of service, and excessive CPU consumption.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

0.94%

56.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-835

Affected Software

Vendor	Product	Versions
Contiki-Os	Contiki	3.0

References

https://github.com/contiki-os/contiki/issues/2685Exploit, Issue Tracking, Patch, Third Party Advisory
https://github.com/contiki-os/contiki/issues/2685Exploit, Issue Tracking, Patch, Third Party Advisory

Timeline

Published: Aug 9, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-38311?

How severe is CVE-2021-38311?

CVE-2021-38311 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.94% probability of exploitation in the next 30 days.

How do I fix CVE-2021-38311?

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-2021-38311?

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

Scan your code now

Source: NVD / NIST