{"api_version":"1","generated_at":"2026-10-09T21:33:04+00:00","cve":"CVE-2026-107838","urls":{"html":"https://cve.report/CVE-2026-107838","api":"https://cve.report/api/cve/CVE-2026-107838.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-107838","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-107838"},"summary":{"title":"RIOT: nanocoap_fileserver ignores response initialization failure, leading to reachable assertion","description":"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/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. 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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."}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-252","description":"CWE-252: Unchecked Return Value","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-617","description":"CWE-617: Reachable Assertion","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-10-09T17:55:34.670Z","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M"},"references":[{"name":"https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-39j3-3v73-5mj2","tags":["x_refsource_CONFIRM"],"url":"https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-39j3-3v73-5mj2"},{"name":"https://github.com/RIOT-OS/RIOT/pull/22745","tags":["x_refsource_MISC"],"url":"https://github.com/RIOT-OS/RIOT/pull/22745"},{"name":"https://github.com/RIOT-OS/RIOT/commit/d3a47289c58d108575a19e623e4d3f647659e743","tags":["x_refsource_MISC"],"url":"https://github.com/RIOT-OS/RIOT/commit/d3a47289c58d108575a19e623e4d3f647659e743"}],"source":{"advisory":"GHSA-39j3-3v73-5mj2","discovery":"UNKNOWN"},"title":"RIOT: nanocoap_fileserver ignores response initialization failure, leading to reachable assertion"}},"cveMetadata":{"assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","assignerShortName":"GitHub_M","cveId":"CVE-2026-107838","datePublished":"2026-10-09T17:55:34.670Z","dateReserved":"2026-10-08T22:34:49.290Z","dateUpdated":"2026-10-09T17:55:34.670Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-09 18:17:05","lastModifiedDate":"2026-10-09 18:17:05","problem_types":["CWE-252","CWE-617","CWE-252 CWE-252: Unchecked Return Value","CWE-617 CWE-617: Reachable Assertion"],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":3.6}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"107838","Ordinal":"1","Title":"RIOT: nanocoap_fileserver ignores response initialization failur","CVE":"CVE-2026-107838","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"107838","Ordinal":"1","NoteData":"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/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.","Type":"Description","Title":"RIOT: nanocoap_fileserver ignores response initialization failur"}]}}}