CVE-2026-27703: Riot-OS Riot

Critical severity, CVSS 9.8. EPSS: 0.6% chance of exploitation in the next 30 days.

RIOT is an open-source microcontroller operating system, designed to match the requirements of Internet of Things (IoT) devices and other embedded devices. In 2026.01 and earlier, the default handler for the well_known_core resource coap_well_known_core_default_handler writes user-provided option data and other data into a fixed size buffer without validating the buffer is large enough to contain the response. This vulnerability allows an attacker to corrupt neighboring stack location, including security-sensitive addresses like the return address, leading to denial of service or arbitrary code execution.

Affected products

• Riot-OS Riot: up to and including 2026.01

Published 2026-03-11. Last modified 2026-06-17.