vulnerability
Ubuntu: (CVE-2021-32677): fastapi vulnerability
| Severity | CVSS | Published | Added | Modified |
|---|---|---|---|---|
| 6 | (AV:N/AC:M/Au:N/C:P/I:P/A:N) | Jun 9, 2021 | Jun 26, 2025 | Mar 27, 2026 |
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.
Solution
References
- CVE-2021-32677
- https://attackerkb.com/topics/CVE-2021-32677
- CWE-352
- EUVD-EUVD-2021-0080
- https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-0080
- https://github.com/tiangolo/fastapi/commit/fa7e3c996edf2d5482fff8f9d890ac2390dede4d
- https://github.com/tiangolo/fastapi/security/advisories/GHSA-8h2j-cgx8-6xv7
- https://www.cve.org/CVERecord?id=CVE-2021-32677
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