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Vulnerability record · CVE-2025-66647 · published 17 December 2025

CVE-2025-66647: Riot-os riot classic buffer overflow 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 copying the contents of the first fragment (offset=0) into the reassembly buffer, no size check is performed. It is possible to force the creation of a small reassembly buffer by first sending a shorter fragment (also with offset=0). Overflowing the reassembly buffer corrupts the state of other packet buffers which an attacker might be able to used to achieve further memory corruption (potentially resulting in remote code execution). To trigger the vulnerability, the `gnrc_ipv6_ext_frag` module must be included and the attacker must be able to send arbitrary IPv6 packets to the victim. Version 2025.10 fixes the issue.

1.7 CVSS 4.0 Low EPSS 0.97% · top 38.8% CWE-120 · Classic buffer overflow
1.7CVSS 4.0 base score
0.97%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References, 1 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 copying the contents of the first fragment (offset=0) into the reassembly buffer, no size check is performed. It is possible to force the creation of a small reassembly buffer by first sending a shorter fragment (also with offset=0). Overflowing the reassembly buffer corrupts the state of other packet buffers which an attacker might be able to used to achieve further memory corruption (potentially resulting in remote code execution). To trigger the vulnerability, the `gnrc_ipv6_ext_frag` module must be included and the attacker must be able to send arbitrary IPv6 packets to the victim. Version 2025.10 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/releases/tag/2025.10 Release Notes
https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-wh3v-q6vr-j79r ExploitPatchVendor Advisory

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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-2021-27698Riot-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%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%

Source: NIST National Vulnerability Database (record CVE-2025-66647), CISA KEV, FIRST EPSS (scores of 2026-10-15). This page is refreshed as NVD updates the record.