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

Why it is Amber

• CVSS 9.1 critical
• Remotely exploitable without logging in

References

• https://github.com/RIOT-OS/RIOT/commit/6b283ace3565d931b3edff7e115d4f79339253b8
• https://github.com/RIOT-OS/RIOT/commit/ee1fa0ef91874494823d476392572aeefdbc6b74
• https://github.com/RIOT-OS/RIOT/releases/tag/2026.07
• https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-8365-gj33-rgpf

Original description

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.