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Vulnerability record · CVE-2025-66646 · published 17 December 2025

CVE-2025-66646: Riot-os riot null pointer dereference vulnerability

Riot Os · Riot

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.

1.7 CVSS 4.0 Low EPSS 0.68% · top 48.8% CWE-476 · NULL pointer dereference
1.7CVSS 4.0 base score
0.68%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
10References, 2 tagged exploit
13 Oct 2026Last modified by NVD

Description

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.

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/g Product
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/g Product
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/g Product
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/g Product
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/g Product
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/g Product
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/pktbuf_static/gnrc_pktbuf_sta Product
https://github.com/RIOT-OS/RIOT/releases/tag/2025.10 Release Notes
https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-v8gx-q9m6-5xm9 ExploitPatchVendor Advisory
https://github.com/user-attachments/files/23903992/reproducer_1.zip Exploit

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2026-27703Riot-os riot out-of-bounds write vulnerabilityRIOT is an open-source microcontroller operating system, designed to match the requirements of Internet of Things (IoT) devices and other embedded de…EPSS 0.62%9.8CVE-2023-33975Riot-os riot memory buffer overflow vulnerabilityRIOT-OS, an operating system for Internet of Things (IoT) devices, contains a network stack with the ability to process 6LoWPAN frames. In version 20…EPSS 1.5%9.8CVE-2023-24823Riot-os riot out-of-bounds write vulnerabilityRIOT-OS, an operating system that supports Internet of Things devices, contains a network stack with the ability to process 6LoWPAN frames. Prior to …EPSS 0.99%9.8CVE-2023-24819Riot-os riot out-of-bounds write vulnerabilityRIOT-OS, an operating system that supports Internet of Things devices, contains a network stack with the ability to process 6LoWPAN frames. Prior to …EPSS 0.99%9.8CVE-2021-27427Riot-os riot integer overflow vulnerabilityRIOT OS version 2020.01.1 is vulnerable to integer wrap-around in its implementation of calloc function, which can lead to arbitrary memory allocatio…EPSS 1.7%9.8CVE-2021-27357Riot-os riot classic buffer overflow vulnerabilityRIOT-OS 2020.01 contains a buffer overflow vulnerability in /sys/net/gnrc/routing/rpl/gnrc_rpl_control_messages.c.EPSS 1.2%9.8CVE-2021-27698Riot-os riot classic buffer overflow vulnerabilityRIOT-OS 2021.01 contains a buffer overflow vulnerability in /sys/net/gnrc/routing/rpl/gnrc_rpl_control_messages.c through the _parse_options() functi…EPSS 1.2%9.8CVE-2021-27697Riot-os riot classic buffer overflow vulnerabilityRIOT-OS 2021.01 contains a buffer overflow vulnerability in sys/net/gnrc/routing/rpl/gnrc_rpl_validation.c through the gnrc_rpl_validation_options() …EPSS 1.3%

Source: NIST National Vulnerability Database (record CVE-2025-66646), CISA KEV, FIRST EPSS (scores of 2026-10-14). This page is refreshed as NVD updates the record.