{"id":"CVE-2025-66646","title":"RIOT is an open-source microcontroller operating system, designed to match the requirements of Internet of Things (IoT) devices and other embedded devices","summary":"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 implementatio…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-476"],"vendor":"riot-os","product":"riot","affected":["riot < 2025.10","riot = 2025.10"],"patched":["riot 2025.10"],"published":"2025-12-17","updated":"2026-10-13","sourceUpdated":"2026-10-13T11:10:00.203","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2025-66646","references":[{"url":"https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L411","label":"security-advisories@github.com"},{"url":"https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L420","label":"security-advisories@github.com"},{"url":"https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L490","label":"security-advisories@github.com"},{"url":"https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L532","label":"security-advisories@github.com"},{"url":"https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L534","label":"security-advisories@github.com"},{"url":"https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L544","label":"security-advisories@github.com"},{"url":"https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/pktbuf_static/gnrc_pktbuf_static.c#L150C1-L150C76","label":"security-advisories@github.com"},{"url":"https://github.com/RIOT-OS/RIOT/releases/tag/2025.10","label":"security-advisories@github.com"},{"url":"https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-v8gx-q9m6-5xm9","label":"security-advisories@github.com"},{"url":"https://github.com/user-attachments/files/23903992/reproducer_1.zip","label":"security-advisories@github.com"}],"tags":["nvd"],"epss":0.00679,"epssPercentile":0.50995,"ingestedAt":"2026-10-13T11:23:51.124Z","slug":"CVE-2025-66646","body":"## Overview\n\nRIOT 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.\n\n## Affected\n\n- `riot < 2025.10`\n- `riot = 2025.10`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `riot 2025.10`","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}