CVE-2021-32677: 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…

PriorityP337high8.1CVSS 3.1

AVNACLPRNUIRSUCHIHAN

EPSS

0.77%

52.1th percentile

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.

Affected

7 ranges

Vendor	Product	Version range	Fixed in
debian	fastapi	< fastapi 0.70.0-1 (bookworm)	fastapi 0.70.0-1 (bookworm)
fedoraproject	fedora	—	—
tiangolo	fastapi	< 0.65.2	0.65.2
tiangolo	fastapi	>= 0 < 0.70.0-1	0.70.0-1
tiangolo	fastapi	>= 0 < 0.70.0-1	0.70.0-1
tiangolo	fastapi	>= 0 < 0.70.0-1	0.70.0-1
tiangolo	fastapi	>= 0 < 0.65.2	0.65.2

CVSS provenance

nvdv3.18.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

nvdv2.05.8MEDIUMAV:N/AC:M/Au:N/C:P/I:P/A:N

osv8.1HIGH

vendor_debian8.2HIGH

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