Vulnerability Description
FastAPI is a web framework for building APIs with Python 3.6+ based on standard Python type hints. 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). A request with a content type of text/plain containing JSON data would be accepted and the JSON data would be extracted. Requests with content type text/plain are exempt from CORS preflights, for being considered Simple requests. The browser will 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. 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. It's best to upgrade to the latest FastAPI, but if updating is not possible then 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 can act as a mitigating workaround.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Tiangolo | Fastapi | < 0.65.2 |
| Fedoraproject | Fedora | 34 |
Related Weaknesses (CWE)
References
- https://github.com/tiangolo/fastapi/commit/fa7e3c996edf2d5482fff8f9d890ac2390dedPatchThird Party Advisory
- https://github.com/tiangolo/fastapi/security/advisories/GHSA-8h2j-cgx8-6xv7Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://github.com/tiangolo/fastapi/commit/fa7e3c996edf2d5482fff8f9d890ac2390dedPatchThird Party Advisory
- https://github.com/tiangolo/fastapi/security/advisories/GHSA-8h2j-cgx8-6xv7Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
FAQ
What is CVE-2021-32677?
CVE-2021-32677 is a vulnerability with a CVSS score of 8.2 (HIGH). FastAPI is a web framework for building APIs with Python 3.6+ based on standard Python type hints. FastAPI versions lower than 0.65.2 that used cookies for authentication in path operations that recei...
How severe is CVE-2021-32677?
CVE-2021-32677 has been rated HIGH with a CVSS base score of 8.2/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2021-32677?
Check the references section above for vendor advisories and patch information. Affected products include: Tiangolo Fastapi, Fedoraproject Fedora.