CVE-2025-66646 - Vulnerability Details

- RIOT-OS has NULL pointer dereference in gnrc_ipv6_ext_frag_reass

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 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.

Published: 2025-12-17

Score: 1.7 Low

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Analysis and contextual insights are available on OpenCVE Cloud.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

RIOT-OS

RIOT

affected

Version	Status	Constraints
`< 2025.10`	affected	—

Configuration 1 [-]

OR	cpe:2.3:o:riot-os:riot::::::::
	cpe:2.3:o:riot-os:riot:2025.10:rc1::::::
	cpe:2.3:o:riot-os:riot:2025.10:rc2::::::
	cpe:2.3:o:riot-os:riot:2025.10:rc3::::::

No data.

Vendor	Product	Confidence	Versions
Riot-os	Riot	—	—

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Remediation

No vendor fix or workaround currently provided.

Additional remediation guidance may be available on OpenCVE Cloud.

Tracking

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Advisories

No advisories yet.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact Low

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00207.

Exploitation none

Automatable no

Technical Impact partial

References

Link	Providers
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L411
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L420
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L490
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L532
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L534
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L544
https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/pktbuf_static/gnrc_pktbuf_static.c#L150C1-L150C76
https://github.com/RIOT-OS/RIOT/releases/tag/2025.10
https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-v8gx-q9m6-5xm9
https://github.com/user-attachments/files/23903992/reproducer_1.zip

History

Thu, 22 Jan 2026 16:30:00 +0000

Type	Values Removed	Values Added
CPEs		cpe:2.3:o:riot-os:riot:::::::: cpe:2.3:o:riot-os:riot:2025.10:rc1:::::: cpe:2.3:o:riot-os:riot:2025.10:rc2:::::: cpe:2.3:o:riot-os:riot:2025.10:rc3::::::
Metrics		cvssV3_1 `{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}`

Thu, 18 Dec 2025 10:00:00 +0000

Type	Values Removed	Values Added
First Time appeared		Riot-os Riot-os riot
Vendors & Products		Riot-os Riot-os riot

Wed, 17 Dec 2025 21:15:00 +0000

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Wed, 17 Dec 2025 19:30:00 +0000

Type	Values Removed	Values Added
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 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.
Title		RIOT-OS has NULL pointer dereference in gnrc_ipv6_ext_frag_reass
Weaknesses		CWE-476
References		https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L411 https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L420 https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L490 https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L532 https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L534 https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/network_layer/ipv6/ext/frag/gnrc_ipv6_ext_frag.c#L544 https://github.com/RIOT-OS/RIOT/blob/eb65305cf9f1b7affb50b17af5c12341b83a8636/sys/net/gnrc/pktbuf_static/gnrc_pktbuf_static.c#L150C1-L150C76 https://github.com/RIOT-OS/RIOT/releases/tag/2025.10 https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-v8gx-q9m6-5xm9 https://github.com/user-attachments/files/23903992/reproducer_1.zip
Metrics		cvssV4_0 `{'score': 1.7, 'vector': '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'}`

Subscriptions

Riot-os Riot

MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2025-12-17T19:18:08.696Z

Updated: 2025-12-17T20:30:49.970Z

Reserved: 2025-12-05T20:23:19.595Z

Link: CVE-2025-66646

Vulnrichment

Updated: 2025-12-17T20:26:58.340Z

NVD

Status : Analyzed

Published: 2025-12-17T20:15:56.170

Modified: 2026-01-22T16:22:00.240

Link: CVE-2025-66646

Redhat

No data.

OpenCVE Enrichment

Updated: 2025-12-18T09:57:07Z

Weaknesses

CWE-476

Tracking

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact Low

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

Exploitation none

Automatable no

Technical Impact partial

Subscriptions

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