ByteDance DeerFlow Path Traversal and Arbitrary File Write via Bootstrap Mode

{
  "id": "0716a29b8d4c5b382e9576180fe8191ed73feec543ad8e1f0e4380d9e7be0d75",
  "url": "https://osv.dev/vulnerability/CVE-2026-40518",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ByteDance DeerFlow Path Traversal and Arbitrary File Write via Bootstrap Mode",
    "summary": "ByteDance DeerFlow before commit 2176b2b contains a path traversal and arbitrary file write vulnerability in bootstrap-mode custom-agent creation where the agent name validation is bypassed. Attackers can supply traversal-style values or absolute paths as the agent name to influence directory creation and write files outside the intended custom-agent directory, potentially achieving arbitrary file write on the system subject to filesystem permissions.",
    "evidence": "osv:CVE-2026-40518",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-40518",
      "aliases": [
        "CVE-2026-40518"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/bytedance/deer-flow",
              "type": "GIT",
              "events": [
                {
                  "introduced": "7e7f0410797693cf882594555ba414e0361d4c6f"
                },
                {
                  "fixed": "2176b2bbfccfce25ceee08318813f96d843a13fd"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:bytedance:deerflow:2.0-m0:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.0-m0"
                      },
                      {
                        "last_affected": "2.0-m0"
                      }
                    ],
                    "source": "CPE_STRING"
                  },
                  {
                    "range": [
                      {
                        "fixed": "2176b2bbfccfce25ceee08318813f96d843a13fd"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "2.0-m0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-40518.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:49.176831386Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40518.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-40518",
        "https://www.vulncheck.com/advisories/bytedance-deerflow-path-traversal-and-arbitrary-file-write-via-bootstrap-mode",
        "https://github.com/bytedance/deer-flow/pull/2274",
        "https://github.com/bytedance/deer-flow/commit/2176b2bbfccfce25ceee08318813f96d843a13fd",
        "https://github.com/bytedance/deer-flow"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-22"
        ],
        "cna_assigner": "VulnCheck",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40518.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-40518",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 517359,
  "published_at": "2026-04-17T16:43:42.387+00:00"
}