CVE-2025-66647: RIOT · Classic Buffer Overflow
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, 09:15 UTC
- EPSS
- 0.9% chance of exploitation in 30 days – higher than 61% 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 26 Oct 2026.
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
1. Upgrade all RIOT-OS deployments to version 2025.10 or later, where the vulnerability is patched. 2. Disable the gnrc_ipv6_ext_frag module if IPv6 fragmentation is not required in the deployment environment to reduce the attack surface. 3. Implement strict network segmentation and firewall rules to limit exposure of IoT devices to untrusted IPv6 traffic, especially from external networks. 4. Monitor network traffic for anomalous IPv6 fragmentation patterns that could indicate exploitation attempts. 5. Employ intrusion detection systems capable of inspecting IPv6 fragmented packets for suspicious behavior. 6. Conduct regular firmware audits and vulnerability assessments on IoT devices to ensure timely patching and configuration compliance. 7. Collaborate with device manufacturers and vendors to ensure secure update mechanisms are in place for rapid deployment of patches.
Description
CVE-2025-66647 is a buffer overflow vulnerability in the IPv6 fragmentation reassembly implementation of RIOT-OS versions prior to 2025.10. The flaw occurs because the system does not check the size when copying the first IPv6 fragment into the reassembly buffer, allowing an attacker to overflow this buffer by manipulating fragment sizes. This overflow can corrupt adjacent packet buffers, potentially enabling further memory corruption and remote code execution. Exploitation requires the vulnerable gnrc_ipv6_ext_frag module to be enabled and the ability to send arbitrary IPv6 packets to the target device. Although the CVSS score is low (1.7), the vulnerability could be critical in specific IoT contexts where RIOT-OS is deployed. The issue is fixed in version 2025.10, and no known exploits are currently reported in the wild.
References
- github.com/RIOT-OS/RIOT/security/advisories/GHSA-wh3v-q6vr-j79r (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/releases/tag/2025.10 (opens in a new tab)