GHSA-2gxp-6r36-m97r
HIGHCadwyn vulnerable to XSS on the docs page
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
cadwynReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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)+'',
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | cadwyn | all versions | 5.4.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for cadwyn. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update cadwyn to 5.4.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-2gxp-6r36-m97r is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-2gxp-6r36-m97r is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-2gxp-6r36-m97r. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-2gxp-6r36-m97r in your dependencies?
O3 detects GHSA-2gxp-6r36-m97r across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.