{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "source": "REFERENCES"
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "f1673b5766d4d4d514cefb8a0350f43653574997"
            }
          ],
          "repo": "https://github.com/contiki-ng/contiki-ng",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "VulnCheck",
    "cwe_ids": [
      "CWE-125"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5855.json",
    "unresolved_ranges": [
      {
        "extracted_events": [
          {
            "fixed": "f1673b5766d4d4d514cefb8a0350f43653574997"
          }
        ],
        "source": "AFFECTED_FIELD"
      }
    ]
  },
  "details": "Contiki-NG's LwM2M TLV parser lwm2m_tlv_read() in os/services/lwm2m/lwm2m-tlv.c ignores its caller-supplied buffer length argument and reads up to six bytes from the input buffer with no bounds check. The caller in lwm2m-engine.c iterates while there is at least one byte remaining, so a crafted CoAP WRITE to any LwM2M endpoint whose final TLV supplies exactly one byte triggers up to five out-of-bounds reads of heap memory adjacent to the CoAP input buffer, disclosing memory contents (including key material and peer addresses) through the parsed tlv-\u003eid, tlv-\u003elength, and tlv-\u003evalue fields. Corrupted tlv_len derived from the out-of-bounds memory further corrupts the caller's parse offset. In LwM2M NoSec mode, the default for constrained devices, no authentication is required.",
  "id": "CVE-2026-5855",
  "modified": "2026-08-09T03:30:21.778756521Z",
  "published": "2026-08-06T18:39:06.869Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5855.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-5855"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/contiki-ng/contiki-ng/pull/3165"
    },
    {
      "type": "FIX",
      "url": "https://github.com/contiki-ng/contiki-ng/commit/f1673b5766d4d4d514cefb8a0350f43653574997"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/contiki-ng/contiki-ng"
    }
  ],
  "schema_version": "1.8.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Contiki-NG LwM2M TLV Parser Out-of-Bounds Read via Unchecked Buffer Length in lwm2m_tlv_read"
}