RIOT OS Patch Fixes Critical CoAP Memory Corruption Flaw
A critical vulnerability in RIOT OS allowed remote attackers to trigger memory corruption via malformed CoAP Block2 options.
Key points
- CVE-2026-102699 is rated CVSS 9.1 Critical for RIOT OS versions prior to 2026.07.
- The flaw involves integer overflow in nanocoap when processing oversized Block2 options.
- Attackers can cause out-of-bounds memory access, denial of service, or memory corruption.
RIOT OS version 2026.07 addresses a critical vulnerability that allowed remote attackers to corrupt memory or crash embedded devices. The issue, tracked as CVE-2026-102692, affects the nanocoap component of the open-source microcontroller operating system designed for Internet of Things devices.
At a glance
- CVE
- CVE-2026-102692
- Product
- RIOT-OS RIOT
- CVSS
- 9.1 Critical
- Weakness
- out-of-bounds write
- Exploited
- No known exploitation
The vulnerability stems from nanocoap accepting oversized CoAP Block2 option values without enforcing the standard 20-bit maximum block number. According to the National Vulnerability Database record, this lack of validation allows block offset multiplication to overflow on 32-bit targets. The oversized value passes from coap_get_blockopt() to coap_block_slicer_init(), creating conditions for exploitation.
Technical details and impact
The NVD rates CVE-2026-102692 as Critical with a CVSS score of 9.1. The weaknesses are classified under CWE-190 (Integer Overflow or Wraparound) and CWE-787 (Out-of-bounds Write). A remote CoAP client can send a malformed Block2 option that produces an invalid slice range. This action can lead to out-of-bounds memory access, denial of service, or memory corruption on the affected device.
The affected master baseline is commit aeeae69e. The verified fix is located later on the master branch and remains unreleased in older versions. The vulnerability is fully fixed in RIOT OS version 2026.07. Devices running versions prior to 2026.07 are susceptible to this remote attack vector.
Who is affected
RIOT OS is an open-source microcontroller operating system designed for Internet of Things devices and other embedded systems. Any deployment using RIOT OS versions earlier than 2026.07 is affected by this vulnerability. The flaw specifically impacts systems using the nanocoap library for handling Constrained Application Protocol communications.
Embedded systems that rely on CoAP for remote management or data exchange are at risk. Attackers do not need authentication to exploit this flaw, as it can be triggered by a remote CoAP client sending a single malformed packet. Organizations managing large fleets of IoT devices should verify their RIOT OS versions immediately.
What should you do?
Security teams should audit their inventory of RIOT OS-based devices to identify versions prior to 2026.07. Since a fix is available, upgrading to version 2026.07 is the primary mitigation strategy. Until updates are applied, network segmentation can help limit exposure to untrusted CoAP clients.
What to do and how to stay safe: RIOT OS
- Inventory all devices running RIOT OS and check for versions earlier than 2026.07.
- Apply the update to RIOT OS version 2026.07 to patch the nanocoap vulnerability.
- Monitor network logs for unusual CoAP Block2 option values or malformed packets.
- Restrict CoAP access to trusted clients using firewall rules if immediate patching is not possible.
Step-by-step guide: Risk-Based Vulnerability Management: Prioritize Fixes by Actual Danger
General security guidance from the Threat Times newsroom. It is not confirmed advice from the organisations named in this story.
Frequently asked questions
What is the CVSS score for CVE-2026-102692?
The National Vulnerability Database rates CVE-2026-102692 as Critical with a CVSS score of 9.1.
Which RIOT OS versions are affected by this vulnerability?
All RIOT OS versions prior to 2026.07 are affected by this critical memory corruption flaw.
Is there a fix available for this issue?
Yes, the vulnerability is fixed in RIOT OS version 2026.07 and in later commits on the master branch.
