NULL pointer dereference in Riot-Os Riot
CVE-2025-66646
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.
EPSS: 0.006 (44.9th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
Affected products
- Riot-os Riot — versions < 2025.10, 2025.10
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Patch, Vendor Advisory)
- security-advisories@github.com (Product, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC)
- security-advisories@github.com (Product, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
- security-advisories@github.com (Exploit, x_refsource_MISC)
Frequently asked questions
- What is CVE-2025-66646?
- CVE-2025-66646 is a high-severity vulnerability in Riot-Os Riot, classified under NULL Pointer Dereference. CVSS score: 7.5/10. Published 2025-12-17.
- How severe is CVE-2025-66646?
- High severity. CVSS v3 base score is 7.5 out of 10.