CVE-2025-66646: RIOT is an open-source microcontroller operating system, designed to match the requirements of Internet of Things…
CVE-2025-66646 · Severity: high · CVSS 7.5 · Published 2025-12-17
RIOT is an open-source microcontroller operating system, designed to match the requirements of Internet of Things (IoT) devices and other embedded devices. A vulnerability was discovered in the IPv6 fragmentation reassembly implementation of RIOT OS v2025.07. When receiving an fragmented IPv6 packet with fragment offset 0 and an empty payload, the payload pointer is set to NULL. However, the implementation still tries to copy the payload into the reassembly buffer, resulting in a NULL pointer dereference which crashes the OS (DoS). To trigger the vulnerability, the `gnrc_ipv6_ext_frag` module must be enabled and the attacker must be able to send arbitrary IPv6 packets to the victim. RIOT OS v2025.10 fixes the issue.
No. Junglewise Threat Intelligence has no report of CVE-2025-66646 being exploited in the wild.
How severe is CVE-2025-66646?
High severity, with a CVSS score of 7.5, published 17 December 2025.
Which products and versions are affected?
Riot-Os Riot. The advisory does not name versions.
Is there a fix for CVE-2025-66646?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
Am I affected by CVE-2025-66646?
Check whether you run Riot-Os Riot. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.