CVE-2026-27703: RIOT has an Out-of-Bounds Write in nanoCoAP Handler
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 wellknowncore resource coapwellknowncoredefaulthandler 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 Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-27703?
CVE-2026-27703 has been classified with a high severity due to the potential for an out-of-bounds write vulnerability.
How do I fix CVE-2026-27703?
To fix CVE-2026-27703, update your RIOT OS to version 2026.02 or later where the vulnerability has been addressed.
What impact does CVE-2026-27703 have on devices running RIOT OS?
CVE-2026-27703 could allow attackers to exploit the out-of-bounds write, leading to potential arbitrary code execution or crashes.
Is CVE-2026-27703 applicable to all versions of RIOT OS?
CVE-2026-27703 is applicable to RIOT OS versions up to and including 2026.01.
Who is affected by CVE-2026-27703?
Developers and users of RIOT OS prior to version 2026.02 are affected by CVE-2026-27703.