CVE-2025-66646Public exploitNetwork attack vector

Firmware crash via empty IPv6 fragment reassembly

Published Dec 17, 2025 · Updated Dec 17, 2025

NULL pointer dereference in RIOT before 2025.10 allows remote attackers to crash device firmware with crafted IPv6 fragments. The gnrc_ipv6_ext_frag_reass function retains a NULL data pointer after stripping an empty fragment header, then passes that pointer as memcpy's reassembly-buffer destination when a second offset-zero fragment arrives. Exploitation requires the gnrc_ipv6_ext_frag module and arbitrary IPv6 packet delivery; the result is an immediate firmware crash rather than data access or modification.

CVSS severity7.5
High
EPSS probability0.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in RIOT before 2025.10 allows remote attackers to crash device firmware with crafted IPv6 fragments. The gnrc_ipv6_ext_frag_reass function retains a NULL data pointer after stripping an empty fragment header, then passes that pointer as memcpy's reassembly-buffer destination when a second offset-zero fragment arrives. Exploitation requires the gnrc_ipv6_ext_frag module and arbitrary IPv6 packet delivery; the result is an immediate firmware crash rather than data access or modification.

The record

CVE
CVE-2025-66646
Published
Dec 17, 2025
Updated
Dec 17, 2025
Vendor
RIOT-OS
Product
RIOT
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 17, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 17, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2025.10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

RIOT-OS · RIOTversion=< 2025.10

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
1.7GitHub, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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