{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0.11.0"
              },
              {
                "fixed": "5.0.8"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "8a14f636b74706cb41c10e8cf27444abc3dc0dac"
            },
            {
              "fixed": "45486556be9d023e194665e243f156b228e195e0"
            },
            {
              "fixed": "c2b1cfd5f5b3530d613c167fc999a7df4eb2eabb"
            }
          ],
          "repo": "https://github.com/fluent/fluent-bit",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-jrp8-r9hx-gf73"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-121",
      "CWE-787",
      "CWE-843"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/61xxx/CVE-2026-61674.json"
  },
  "details": "Fluent Bit is a fast and lightweight logs, metrics, and traces processor for Linux, BSD, macOS, and Windows. From 0.11.0 until 5.0.8, plugins/out_forward/forward.c secure_forward_pong copies the server-controlled PONG[2] reason into the 32-byte stack buffer msg with memcpy without checking its MessagePack type or length. An attacker who controls or can impersonate an out_forward Secure Forward destination configured with Shared_Key or Empty_Shared_Key can send an oversized reason during the first handshake and overwrite stack control data. Protected builds reliably terminate, while builds without a stack canary or with a disclosure can allow remote code execution as the Fluent Bit process user. When the opt-in --supervisor mode is used, fork-only respawns preserve the canary and address layout, allowing repeated crash-or-survive probes to support code execution on a hardened build; ordinary exec-based or service-manager restarts do not preserve that state. This issue is fixed in version 5.0.8.",
  "id": "CVE-2026-61674",
  "modified": "2026-09-26T03:30:50.645308944Z",
  "published": "2026-09-21T16:10:15.276Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/fluent/fluent-bit/releases/tag/v5.0.8"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/61xxx/CVE-2026-61674.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/fluent/fluent-bit/security/advisories/GHSA-jrp8-r9hx-gf73"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-61674"
    },
    {
      "type": "FIX",
      "url": "https://github.com/fluent/fluent-bit/commit/45486556be9d023e194665e243f156b228e195e0"
    },
    {
      "type": "FIX",
      "url": "https://github.com/fluent/fluent-bit/pull/11945"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Fluent Bit: Remote stack buffer overflow in Fluent Bit `out_forward` Secure-Forward `PONG` handler"
}