CVE-2026-8505: Langflow Authentication Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-cf6m-vc3m-7cgm",
  "modified" : "2026-10-05T22:31:22Z",
  "published" : "2026-10-05T22:31:22Z",
  "aliases" : [ "CVE-2026-8505" ],
  "summary" : "Langflow: Unauthenticated Flow Execution via Webhook Authentication Bypass",
  "details" : "### Summary\nA vulnerability in Langflow's webhook authentication logic allows unauthenticated users to trigger the execution of any flow. The system incorrectly bypasses API key validation when the `WEBHOOK_AUTH_ENABLE` configuration is set to `False`. This allows a remote attacker who knows a flow's UUID to execute it as if they were the owner, potentially leading to Remote Code Execution (RCE) or Denial of Service (DoS).\n\n### Details\nThe `WEBHOOK_AUTH_ENABLE` setting was introduced in v1.7.0 (#9139) with a default of `False`. The root cause is in the webhook authentication path, `AuthService.get_webhook_user` (`src/backend/base/langflow/services/auth/service.py`; the thin wrapper in `src/backend/base/langflow/services/auth/utils.py` just delegates to it):\n\n```python\nasync def get_webhook_user(self, flow_id: str, request: Request) -> UserRead:\n    settings_service = self.settings\n    ...\n    # VULNERABILITY: If this setting is False (default in <= 1.9.0), it returns\n    # the flow owner WITHOUT checking the API Key in the request.\n    if not settings_service.auth_settings.WEBHOOK_AUTH_ENABLE:\n        try:\n            flow_owner = await get_user_by_flow_id_or_endpoint_name(flow_id)\n            return flow_owner\n```\n\nBy default (v1.7.0 through v1.9.0), Langflow treats `WEBHOOK_AUTH_ENABLE` as `False`, meaning all webhook endpoints are public. This relies exclusively on the secrecy of the `flow_id` (UUID), which is an insecure practice (Security by Obscurity).\n\nA related report, GHSA-6g4m-v5q2-475v, demonstrated a concrete RCE chain through this same bypass using the `PythonCodeStructuredTool` component (`exec()` on flow-authored Python code). That report is a duplicate of this root cause and has been closed in favor of this advisory; credit for that PoC has been added here.\n\n### PoC\n1. Identify a valid `flow_id` for a flow that performs a sensitive action (e.g., sending an email, writing to a database, or executing a Python script).\n2. Execute a POST request to the webhook endpoint without any `Authorization` header or API Key:\n```bash\ncurl -X POST \"http://<server-ip>:7860/api/v1/webhook/<flow_id>\" \\\n     -H \"Content-Type: application/json\" \\\n     -d '{\"input\": \"payload\"}'\n```\n3. Verify that the flow execution is triggered and the action is performed on the server.\n\n### Impact\nThis is a **High-severity Authentication Bypass**.\n- **Remote Code Execution (RCE)**: Flows often contain components that execute arbitrary Python code. An attacker can leverage this to gain full control over the server.\n- **Denial of Service (DoS)**: Attackers can exhaust system resources by triggering heavy flows concurrently.\n- **Data Integrity**: Unauthorized execution of flows can lead to unintended modification of databases or external systems connected via the flow.\n\n### Affected versions\n`>= 1.7.0, <= 1.9.0` (the range in which `WEBHOOK_AUTH_ENABLE` existed and defaulted to `False`).\n\n### Fix\nFixed in **v1.9.1** by [PR #12845](https://github.com/langflow-ai/langflow/pull/12845) — `fix(security): default WEBHOOK_AUTH_ENABLE to True`. The setting's default changed from `False` to `True`, so webhook endpoints now require API key authentication and ownership validation by default, unless an operator explicitly opts out via `LANGFLOW_WEBHOOK_AUTH_ENABLE=false`.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "langflow"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.7.0"
      }, {
        "fixed" : "1.9.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.9.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/langflow-ai/langflow/security/advisories/GHSA-cf6m-vc3m-7cgm"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-8505"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/langflow-ai/langflow/pull/12845"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/langflow-ai/langflow/commit/cb6f7508dda83ead9c3e4417e96e4b5bd9a260c3"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/langflow-ai/langflow"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/langflow-ai/langflow/releases/tag/v1.9.1"
  }, {
    "type" : "WEB",
    "url" : "https://www.ibm.com/support/pages/node/7278921"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-306" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-05T22:31:22Z",
    "nvd_published_at" : null
  }
}