{"id":"CVE-2026-107838","title":"RIOT is an open-source microcontroller operating system designed for Internet of Things devices and other embedded systems","summary":"RIOT is an open-source microcontroller operating system designed for Internet of Things devices and other embedded systems. From version 2023.07 through version 2026.07, nanocoap_fileserver callers in sys/net/application_layer/nanocoap/f…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-252","CWE-617"],"published":"2026-10-09","updated":"2026-10-09","sourceUpdated":"2026-10-09T18:17:05.640","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-107838","references":[{"url":"https://github.com/RIOT-OS/RIOT/commit/d3a47289c58d108575a19e623e4d3f647659e743","label":"security-advisories@github.com"},{"url":"https://github.com/RIOT-OS/RIOT/pull/22745","label":"security-advisories@github.com"},{"url":"https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-39j3-3v73-5mj2","label":"security-advisories@github.com"}],"tags":["nvd"],"ingestedAt":"2026-10-09T19:09:33.756Z","slug":"CVE-2026-107838","body":"## Overview\n\nRIOT is an open-source microcontroller operating system designed for Internet of Things devices and other embedded systems. From version 2023.07 through version 2026.07, nanocoap_fileserver callers in sys/net/application_layer/nanocoap/fileserver.c ignore a failure returned by _resp_init() when coap_build_reply() cannot fit a response header into the response buffer. A remote client can send a CoAP request with a sufficiently large extended token when nanocoap_token_ext is enabled, causing response initialization to fail while _get_file() or _get_directory() continues with stale response state. The path then reaches _calc_szx2() and its pdu->payload_len > reserve assertion, terminating the affected service or device task. No fixed release is available as of this review.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}