CVE-2021-40523: Contiki-OS Contiki

High severity, CVSS 7.5. EPSS: 1% chance of exploitation in the next 30 days.

In Contiki 3.0, Telnet option negotiation is mishandled. During negotiation between a server and a client, the server may fail to give the WILL/WONT or DO/DONT response for DO and WILL commands because of improper handling of exception condition, which leads to property violations and denial of service. Specifically, a server sometimes sends no response, because a fixed buffer space is available for all responses and that space may have been exhausted.

Affected products

• Contiki-OS Contiki: version 3.0 only

Published 2021-09-05. Last modified 2026-06-17.