CVE-2025-66646: RIOT · NULL Pointer Dereference
Affects RIOTSource CVE Database V5
Not known to be exploited · CVSS 1.7 Low : upgrade to 2025.10 when convenient.
Data as of 26 Oct 2026, 07:57 UTC
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 52% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 2025.10
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:UExploitation evidence
Disclosed: evidence found.
CVE published 17 Dec 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.
What to do
Upgrade riot-os/RIOT to 2025.10.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
GitHubriot-os/RIOTpkg:github/riot-os/RIOTOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
European organizations should immediately upgrade all RIOT OS deployments to version 2025.10 or later, where the vulnerability is patched. Network administrators should consider filtering or monitoring IPv6 fragmented packets, especially those with fragment offset zero and empty payloads, to detect or block suspicious traffic targeting the gnrc_ipv6_ext_frag module. Implementing network segmentation and limiting exposure of IoT devices to untrusted IPv6 networks can reduce attack surface. Additionally, organizations should audit their IoT device configurations to verify whether the vulnerable IPv6 fragmentation module is enabled and disable it if not required. Regular firmware and OS updates, combined with network-level anomaly detection tailored for IoT traffic patterns, will further mitigate risks from similar vulnerabilities.
Description
CVE-2025-66646 is a low-severity vulnerability in RIOT OS versions prior to 2025.10, affecting the IPv6 fragmentation reassembly module. The flaw is a NULL pointer dereference triggered when a fragmented IPv6 packet with fragment offset 0 and an empty payload is received, causing the OS to crash and resulting in a denial of service (DoS). Exploitation requires the gnrc_ipv6_ext_frag module to be enabled and the attacker to send crafted IPv6 packets to the device. No authentication or user interaction is needed, but the impact is limited to DoS without data compromise. The vulnerability has a CVSS 4.0 score of 1.7, indicating low severity. European organizations using RIOT OS in IoT or embedded devices should update to version 2025.10 to mitigate this issue.
References
- github.com/RIOT-OS/RIOT/security/advisories/GHSA-v8gx-q9m6-5xm9 (opens in a new tab)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c (opens in a new tab)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c (opens in a new tab)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c (opens in a new tab)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c (opens in a new tab)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c (opens in a new tab)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c (opens in a new tab)
- github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/pktbuf_static/gnrc_pktbuf_static.c (opens in a new tab)
- github.com/RIOT-OS/RIOT/releases/tag/2025.10 (opens in a new tab)
- github.com/user-attachments/files/23903992/reproducer_1.zip (opens in a new tab)