---
id: "CVE-2026-102692"
kind: "vulnerability"
aliases: ["CVE-2026-102692"]
title: "RIOT is an open-source microcontroller operating system designed for Internet of Things devices and other embedded\u2026"
severity: "critical"
cvss: 9.1
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["32-bit", "coap", "embedded", "iot", "nanocoap", "riot", "runtime"]
not_affected_if: ["64-bit-target", "default-config", "no-coap-server"]
published_at: "2026-10-16T17:17:16+00:00"
first_seen_at: "2026-10-23T21:57:13+00:00"
updated_at: "2026-10-23T22:28:55+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-102692", "first_seen_at": "2026-10-23T21:57:13+00:00"}]
---

# RIOT is an open-source microcontroller operating system designed for Internet of Things devices and other embedded…

RIOT, an open-source operating system for IoT microcontrollers, has an integer overflow in its nanocoap CoAP server when handling oversized Block2 option values on 32-bit targets. A remote CoAP client can send a malformed Block2 option to cause out-of-bounds memory access, denial of service, or memory corruption.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

Check whether the firmware is built from RIOT master at or after commit aeeae69e and before the fix, or runs a RIOT release before 2026.07.
Check whether the device runs nanocoap on a 32-bit target with a CoAP server listening on the network.

## Fix

Move to RIOT 2026.07 or later, or to a master build that includes the verified fix; the fix is not in a released version before 2026.07.

## Timeline

- 2026-10-23T21:57:13+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-102692

## From the sources

RIOT is an open-source microcontroller operating system designed for Internet of Things devices and other embedded systems. Prior to 2026.07, nanocoap accepts oversized CoAP Block2 option values without enforcing the 20-bit maximum block number, allowing block offset multiplication to overflow on 32-bit targets. The affected master baseline is commit aeeae69e; the verified fix is later on master and remains unreleased. The oversized value passes from coap_get_blockopt() to coap_block_slicer_init(). A remote CoAP client can send a malformed Block2 option that produces an invalid slice range and can cause out-of-bounds memory access, denial of service, or memory corruption. This vulnerability is fixed in 2026.07.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_