GHSA-8h2j-cgx8-6xv7 is a high-severity (CVSS 8.2) Cross-Site Request Forgery (CSRF) vulnerability in fastapi. O3 Security confirms whether GHSA-8h2j-cgx8-6xv7 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Cross-Site Request Forgery (CSRF) in FastAPI
Real-World Exposure
fastapiReal-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
Impact
FastAPI versions lower than 0.65.2 that used cookies for authentication in path operations that received JSON payloads sent by browsers were vulnerable to a Cross-Site Request Forgery (CSRF) attack.
In versions lower than 0.65.2, FastAPI would try to read the request payload as JSON even if the content-type header sent was not set to application/json or a compatible JSON media type (e.g. application/geo+json).
So, a request with a content type of text/plain containing JSON data would be accepted and the JSON data would be extracted.
But requests with content type text/plain are exempt from CORS preflights, for being considered Simple requests. So, the browser would execute them right away including cookies, and the text content could be a JSON string that would be parsed and accepted by the FastAPI application.
Patches
This is fixed in FastAPI 0.65.2.
The request data is now parsed as JSON only if the content-type header is application/json or another JSON compatible media type like application/geo+json.
Workarounds
It's best to upgrade to the latest FastAPI.
But still, it would be possible to add a middleware or a dependency that checks the content-type header and aborts the request if it is not application/json or another JSON compatible content type.
References
For more information
If you have any questions or comments, write to [email protected]
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | fastapi | all versions | 0.65.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fastapi. 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 fastapi to 0.65.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-8h2j-cgx8-6xv7 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-8h2j-cgx8-6xv7 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-8h2j-cgx8-6xv7. 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-8h2j-cgx8-6xv7 in your dependencies?
O3 detects GHSA-8h2j-cgx8-6xv7 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.