External risk intelligence

RIOT OS nanocoap Oversized Option Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-102692

The vulnerability exists in the CoAP protocol implementation within an IoT operating system. While CoAP is designed for network-based machine-to-machine communication in IoT environments, it is often deployed within constrained or local networks rather than directly exposed to the public internet. Internet reachability is possible depending on the specific deployment architecture, but not a universal standard.

Integer Overflow

Halo Surface Signal: 3 out of 5 — possibly public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability has been identified in the RIOT microcontroller operating system, which is used in Internet of Things and embedded devices. This issue could allow remote attackers to cause denial of service or memory corruption by sending specially crafted network requests. The main concern is confirming relevance and exposure due to the nature of IoT device deployments.

Network requests can corrupt memory on IoT devices.
Confirming if these devices are reachable from the internet.
Understand potential impact on connected device operations.

Attack Path

How an attacker could exploit the issue

An attacker could target devices running the RIOT operating system by sending specially crafted network messages. These messages would exploit a flaw in how the system handles CoAP data, specifically the Block2 option. If successful, this could lead to memory corruption or denial of service on the affected device.

Requires network access to the device.
Triggered by sending malformed CoAP Block2 options.
Risk of memory corruption or denial of service.

Live Threat

Current exploitation, exposure, and threat context

A remote attacker could send specially crafted CoAP messages to IoT devices running the affected RIOT operating system. This may lead to memory corruption, denial of service, or unexpected service behavior.

IoT device memory and service availability.
Malformed CoAP Block2 option values.
Denial of service or memory corruption.

Operational Fix

Recommended remediation, mitigation, and detection steps

This critical vulnerability in the nanocoap component of the RIOT operating system affects embedded IoT devices. Owners of affected IoT deployments, likely platform or embedded systems teams, must first identify all instances of the RIOT OS. Confirming network exposure and business criticality will prioritize remediation efforts. Coordination with vendors may be necessary for unreleased fixes.

Embedded system owners should prioritize identification.
Verify network reachability and device criticality.
Plan coordinated vendor updates and deployments.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is RIOT OS and why is it used?

RIOT is an open-source operating system purpose-built for resource-constrained hardware like microcontrollers. It is widely used in Internet of Things (IoT) and embedded projects because it provides efficient networking capabilities, such as CoAP, for small-scale devices that monitor sensors or manage automation tasks.

How does CVE-2026-102692 impact device memory?

This vulnerability involves an integer overflow (CWE-190) and out-of-bounds memory access (CWE-787). Because the nanocoap component fails to limit Block2 option values, a math error occurs during processing. This can overwrite nearby memory or crash the system, leading to unexpected behavior or a denial of service.

What triggers this RIOT OS vulnerability?

An attacker triggers the flaw by sending a specially crafted, malformed CoAP packet to a device. Specifically, the packet must contain an oversized Block2 option value. Simply connecting to the device or using standard, valid CoAP requests does not trigger the bug; it requires these intentionally malformed values to cause the overflow.

Do I need to worry if my device is on a local network?

Halo Surface Signal indicates that while IoT devices often reside on restricted local networks, internet reachability is possible. If your device is accessible from the public internet, the risk is higher. You should assess whether your specific network architecture exposes these nanocoap services to untrusted traffic.

Is there a fix for this RIOT OS issue?

Yes, the vulnerability is resolved in RIOT release 2026.07. To address this, inventory your embedded systems to identify those running older versions, verify their network reachability, and plan a firmware update to the patched release to ensure the nanocoap component properly enforces block number limits.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.