CVE-2025-66647

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 0.8%, top 46% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this week
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
9.8
EG Score
9.8(medium)
EG Risk
44(Track)
EG Risk 44/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
54%
KEV
Not listed

Published

December 17, 2025

Last Modified

January 22, 2026

Advisory Details (6)

Auto-updated Jul 27, 2026
🔬 Proof of concept available. Patch available. Sources: github_release, github.
github Patch Available🟡 PoC Available

buffer overflow in gnrc_ipv6_ext_frag_reass · Advisory · RIOT-OS/RIOT · GitHub

https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-wh3v-q6vr-j79r
github_release Patch Available

Release-2025.10

Patch available: RIOT-OS/RIOT 2025.10

https://github.com/RIOT-OS/RIOT/releases/tag/2025.10
generic

RIOT/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c at eb65305cf9f1b7affb50b17af5c12341b83a8636 · RIOT-OS/RIOT · GitHub

https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L544
generic

RIOT/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c at eb65305cf9f1b7affb50b17af5c12341b83a8636 · RIOT-OS/RIOT · GitHub

https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L532
generic

RIOT/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c at eb65305cf9f1b7affb50b17af5c12341b83a8636 · RIOT-OS/RIOT · GitHub

https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L481
generic

RIOT/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c at eb65305cf9f1b7affb50b17af5c12341b83a8636 · RIOT-OS/RIOT · GitHub

https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L411

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 46× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-27 14:12 UTCEPSS rescore
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  9. 2026-07-23 12:19 UTCOSV refresh
  10. 2026-07-23 03:01 UTCEG score recompute
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  8. 2026-07-06 07:32 UTCOSV refresh
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  72. 2026-05-29 17:24 UTCEG score recompute
  73. 2026-05-29 13:44 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2025-66647?
CVE-2025-66647 is a critical vulnerability published on December 17, 2025. 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…
When was CVE-2025-66647 disclosed?
CVE-2025-66647 was first published in the National Vulnerability Database on December 17, 2025, with the most recent update on January 22, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-66647 actively exploited?
CVE-2025-66647 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 45.6% of all scored CVEs.
What is the CVSS score of CVE-2025-66647?
CVE-2025-66647 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2025-66647?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-66647, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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