Security advisory
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2021-32677
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 10:20 UTC · Revision 1
Source evidence
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.
osv:CVE-2021-32677
Complete source record
{
"id": "5433a0786ba46d48fe0d5ebd73771bd0f033a4b2561f0a36a8eea9f4a96248f4",
"url": "https://osv.dev/vulnerability/CVE-2021-32677",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2021-32677",
"summary": "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.",
"evidence": "osv:CVE-2021-32677",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2021-32677",
"aliases": [
"CVE-2021-32677",
"GHSA-8h2j-cgx8-6xv7",
"PYSEC-2021-100"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/fastapi/fastapi",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "4d91f978d265a5050baeb3d4b3618c2f5cb7995a"
},
{
"fixed": "fa7e3c996edf2d5482fff8f9d890ac2390dede4d"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:tiangolo:fastapi:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "0"
},
{
"fixed": "0.65.2"
}
],
"source": "CPE_RANGE"
},
{
"range": [
{
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],
"source": "REFERENCES_COMMIT"
}
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}
}
],
"versions": [
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"0.30.0",
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"0.29.0",
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"0.27.0",
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"0.24.0",
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"0.22.0",
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"0.20.1",
"0.20.0",
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"0.10.1",
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"0.6.1",
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"0.5.1",
"0.5.0",
"0.4.0",
"0.3.0",
"0.2.1",
"0.2.0",
"0.1.19",
"0.1.17",
"v0.1.16",
"0.1.15",
"0.1.14",
"0.1.13",
"0.1.12",
"0.1.11"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-32677.json"
}
}
],
"modified": "2026-10-20T10:50:12.717499112Z",
"provider": "osv",
"references": [
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MATAWX25TYKNEKLDMKWNLYDB34UWTROA/",
"https://github.com/tiangolo/fastapi/security/advisories/GHSA-8h2j-cgx8-6xv7",
"https://github.com/tiangolo/fastapi/commit/fa7e3c996edf2d5482fff8f9d890ac2390dede4d"
],
"provider_metadata": {
"unresolved_ranges": [
{
"cpes": [
"cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*"
],
"vendor_product": "fedoraproject:fedora",
"extracted_events": [
{
"range": [
{
"introduced": "34"
},
{
"last_affected": "34"
}
],
"source": "CPE_STRING"
}
]
}
]
}
},
"related_cves": [
{
"value": "CVE-2021-32677",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 381398,
"published_at": "2021-06-09T18:15:08.553+00:00"
}