{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "2023.07"
              },
              {
                "fixed": "2026.07"
              }
            ],
            "source": [
              "DESCRIPTION",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "985a38cd09e9532b82dc77c4109da66304c5adb8"
            },
            {
              "fixed": "a897b0498f635654f091bf9f33e9696aa773e886"
            },
            {
              "fixed": "d3a47289c58d108575a19e623e4d3f647659e743"
            }
          ],
          "repo": "https://github.com/riot-os/riot",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-39j3-3v73-5mj2"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-252",
      "CWE-617"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107838.json"
  },
  "details": "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-\u003epayload_len \u003e reserve assertion, terminating the affected service or device task. No fixed release is available as of this review.",
  "id": "CVE-2026-107838",
  "modified": "2026-10-11T02:31:02.714917150Z",
  "published": "2026-10-09T17:55:34.670Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107838.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-39j3-3v73-5mj2"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-107838"
    },
    {
      "type": "FIX",
      "url": "https://github.com/RIOT-OS/RIOT/commit/d3a47289c58d108575a19e623e4d3f647659e743"
    },
    {
      "type": "FIX",
      "url": "https://github.com/RIOT-OS/RIOT/pull/22745"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "RIOT: nanocoap_fileserver ignores response initialization failure, leading to reachable assertion"
}