DoS from MQTT v5.0 Deserialization Fault in core MQTT

{
  "id": "aeb8d0bf3caee264e2c9f25d89cf8167bc87e394bb0a88c62d269960679fef8d",
  "url": "https://osv.dev/vulnerability/CVE-2026-8686",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "DoS from MQTT v5.0 Deserialization Fault in core MQTT",
    "summary": "Missing bounds validation in the MQTT v5.0 property parser in coreMQTT before 5.0.1 allows an MQTT broker to cause a denial of service by sending a crafted packet. To remediate this issue, users should upgrade to v5.0.1.",
    "evidence": "osv:CVE-2026-8686",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-8686",
      "aliases": [
        "CVE-2026-8686",
        "GHSA-6qh9-r6jp-2wxc"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "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"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/freertos/coremqtt",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0dd6943057f3fa9a425ea3e1d5e6bd23f5840fd9"
                },
                {
                  "fixed": "76e9d89cb8e2fb4cff965329d835594cebebf618"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "5.0.0"
                      },
                      {
                        "last_affected": "5.0.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandaloneSingleVersion"
                  },
                  {
                    "range": [
                      {
                        "fixed": "76e9d89cb8e2fb4cff965329d835594cebebf618"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v5.0.1"
                  }
                ]
              }
            }
          ],
          "versions": [
            "5.0.0",
            "v5.0.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-8686.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:30.067314655Z",
      "provider": "osv",
      "references": [
        "https://aws.amazon.com/security/security-bulletins/2026-032-aws/",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/8xxx/CVE-2026-8686.json",
        "https://github.com/FreeRTOS/coreMQTT/security/advisories/GHSA-6qh9-r6jp-2wxc",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-8686",
        "https://github.com/FreeRTOS/coreMQTT/releases/tag/v5.0.1"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-125"
        ],
        "cna_assigner": "AMZN",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/8xxx/CVE-2026-8686.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-8686",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 496901,
  "published_at": "2026-05-15T18:38:10.651+00:00"
}