Know every vulnerabilitybefore it knows you.
DevGuard continuously monitors your dependencies and alerts you when CVEs like this one affect your stack — with real-time threat intelligence built for developers.
GHSA-2gxp-6r36-m97r
No affected components available
Summary
The version parameter of the /docs endpoint is vulnerable to a Reflected XSS (Cross-Site Scripting) attack.
PoC
- Setup a minimal app following the quickstart guide: https://docs.cadwyn.dev/quickstart/setup/
- Click on the following PoC link: http://localhost:8000/docs?version=%27%2balert(document.domain)%2b%27
Impact
Refer to this security advisory for an example of the impact of a similar vulnerability that shares the same root cause.
This XSS would notably allow an attacker to execute JavaScript code on a user's session for any application based on Cadwyn via a one-click attack.
A CVSS for the average case may be: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:L
Details
The vulnerable code snippet can be found in the 2 functions swagger_dashboard and redoc_dashboard: https://github.com/zmievsa/cadwyn/blob/main/cadwyn/applications.py#L387-L413
The implementation uses the get_swagger_ui_html function from FastAPI. This function does not encode or sanitize its arguments before using them to generate the HTML for the swagger documentation page and is not intended to be used with user-controlled arguments.
async def swagger_dashboard(self, req: Request) -> Response:
version = req.query_params.get("version")
if version:
root_path = self._extract_root_path(req)
openapi_url = root_path + f"{self.openapi_url}?version={version}"
oauth2_redirect_url = self.swagger_ui_oauth2_redirect_url
if oauth2_redirect_url:
oauth2_redirect_url = root_path + oauth2_redirect_url
return get_swagger_ui_html(
openapi_url=openapi_url,
title=f"{self.title} - Swagger UI",
oauth2_redirect_url=oauth2_redirect_url,
init_oauth=self.swagger_ui_init_oauth,
swagger_ui_parameters=self.swagger_ui_parameters,
)
return self._render_docs_dashboard(req, cast("str", self.docs_url))
In this case, the openapi_url variable contains the version which comes from a user supplied query string without encoding or sanitisation. The user controlled injection ends up inside of a string in a <script> tag context: https://github.com/fastapi/fastapi/blob/master/fastapi/openapi/docs.py#L132
f"""
...
const ui = SwaggerUIBundle({{
url: '{openapi_url}',
"""
By simply injecting a single quote we can escape from the string context and execute JavaScript like so '+alert(document.domain)+'
The resulting HTML sent back from the server contains the following injection:
const ui = SwaggerUIBundle({
url: '/openapi/flows.json?flows='+alert(document.domain)+'',
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a low impact on the integrity of the data. There is a low impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
Browse More
Continuously monitor your dependencies and get alerted when vulnerabilities like this one affect your stack.
Checkout DevGuard