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.
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.007 (50.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 50.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: +0.000
Affected products
- Riot-Os Riot — versions < 2025.10, 2025.10
Weakness classification (CWE)
References
- github.com/RIOT-OS/RIOT/security/advisories/GHSA-v8gx-q9m6-5xm9 (Exploit, Patch, Vendor Advisory)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/g… (Product)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/g… (Product)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/g… (Product)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/g… (Product)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/g… (Product)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/g… (Product)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/g… (Product)
- github.com/RIOT-OS/RIOT/releases/tag/2025.10 (Release Notes)
- github.com/user-attachments/files/23903992/reproducer_1.zip (Exploit)
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.