{"cve":"CVE-2021-32677","nvd":{"published":"2021-06-09T18:15:08.553","modified":"2026-06-17T03:53:24.237","status":"Modified","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_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","score":8.1},"cwes":["CWE-352"],"references":["https://github.com/tiangolo/fastapi/commit/fa7e3c996edf2d5482fff8f9d890ac2390dede4d","https://github.com/tiangolo/fastapi/security/advisories/GHSA-8h2j-cgx8-6xv7","https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MATAWX25TYKNEKLDMKWNLYDB34UWTROA/","https://github.com/tiangolo/fastapi/commit/fa7e3c996edf2d5482fff8f9d890ac2390dede4d","https://github.com/tiangolo/fastapi/security/advisories/GHSA-8h2j-cgx8-6xv7"],"products":["fedoraproject:fedora","tiangolo:fastapi"],"source":"nvd","synced_at":"2026-10-19T21:20:07.141963181+00:00"},"epss":{"cve":"CVE-2021-32677","score":0.00722,"percentile":0.54012,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-8h2j-cgx8-6xv7","url":"https://osv.dev/vulnerability/GHSA-8h2j-cgx8-6xv7","summary":"Cross-Site Request Forgery (CSRF) in FastAPI","modified":"2026-07-08T06:28:18.554408310Z","packages":[{"ecosystem":"PyPI","name":"fastapi","purl":"pkg:pypi/fastapi","ranges":["<0.65.2"],"fixed":["0.65.2"]}]},{"id":"PYSEC-2021-100","url":"https://osv.dev/vulnerability/PYSEC-2021-100","summary":"","modified":"2023-11-08T04:05:56.616377Z","packages":[{"ecosystem":"PyPI","name":"fastapi","purl":"pkg:pypi/fastapi","ranges":["<0.65.2"],"fixed":["0.65.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}