CVE-2021-32677
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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
OS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| arch | fixed | 0.65.2-1 | |
| debian | bookworm | fixed | 0.70.0-1 |
| debian | bullseye | affected | |
| debian | forky | fixed | 0.70.0-1 |
| debian | sid | fixed | 0.70.0-1 |
| debian | trixie | fixed | 0.70.0-1 |
References
- https://security.archlinux.org/ASA-202107-6
- https://github.com/tiangolo/fastapi/security/advisories/GHSA-8h2j-cgx8-6xv7
- https://nvd.nist.gov/vuln/detail/CVE-2021-32677
- https://github.com/tiangolo/fastapi/commit/fa7e3c996edf2d5482fff8f9d890ac2390dede4d
- https://github.com/pypa/advisory-database/tree/main/vulns/fastapi/PYSEC-2021-100.yaml
- https://github.com/tiangolo/fastapi
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MATAWX25TYKNEKLDMKWNLYDB34UWTROA
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MATAWX25TYKNEKLDMKWNLYDB34UWTROA/
- https://security-tracker.debian.org/tracker/CVE-2021-32677
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.