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Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLThoMmotY2d4OC02eHY3

Cross-Site Request Forgery (CSRF) in FastAPI

Impact

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).

So, a request with a content type of text/plain containing JSON data would be accepted and the JSON data would be extracted.

But requests with content type text/plain are exempt from CORS preflights, for being considered Simple requests. So, the browser would 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.

Patches

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.

Workarounds

It's best to upgrade to the latest FastAPI.

But still, it would be possible to add 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.

References

For more information

If you have any questions or comments, write to [email protected]

Permalink: https://github.com/advisories/GHSA-8h2j-cgx8-6xv7
JSON: https://advisories.ecosyste.ms/api/v1/advisories/MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLThoMmotY2d4OC02eHY3
Source: GitHub Advisory Database
Origin: Unspecified
Severity: High
Classification: General
Published: over 3 years ago
Updated: 7 months ago


CVSS Score: 8.2
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N

Identifiers: GHSA-8h2j-cgx8-6xv7, CVE-2021-32677
References: Repository: https://github.com/tiangolo/fastapi
Blast Radius: 38.0

Affected Packages

pypi:fastapi
Dependent packages: 2,920
Dependent repositories: 43,608
Downloads: 56,928,981 last month
Affected Version Ranges: < 0.65.2
Fixed in: 0.65.2
All affected versions: 0.1.0, 0.1.2, 0.1.3, 0.1.4, 0.1.5, 0.1.6, 0.1.7, 0.1.8, 0.1.9, 0.1.10, 0.1.11, 0.1.12, 0.1.13, 0.1.14, 0.1.15, 0.1.16, 0.1.17, 0.1.18, 0.1.19, 0.2.0, 0.2.1, 0.3.0, 0.4.0, 0.5.0, 0.5.1, 0.6.0, 0.6.1, 0.6.2, 0.6.3, 0.6.4, 0.7.0, 0.7.1, 0.8.0, 0.9.0, 0.9.1, 0.10.0, 0.10.1, 0.10.2, 0.11.0, 0.12.0, 0.12.1, 0.13.0, 0.14.0, 0.15.0, 0.16.0, 0.17.0, 0.18.0, 0.19.0, 0.20.0, 0.20.1, 0.21.0, 0.22.0, 0.23.0, 0.24.0, 0.25.0, 0.26.0, 0.27.0, 0.27.1, 0.27.2, 0.28.0, 0.29.0, 0.29.1, 0.30.0, 0.30.1, 0.31.0, 0.32.0, 0.33.0, 0.34.0, 0.35.0, 0.36.0, 0.37.0, 0.38.0, 0.38.1, 0.39.0, 0.40.0, 0.41.0, 0.42.0, 0.43.0, 0.44.0, 0.44.1, 0.45.0, 0.46.0, 0.47.0, 0.47.1, 0.48.0, 0.49.0, 0.49.1, 0.49.2, 0.50.0, 0.51.0, 0.52.0, 0.53.0, 0.53.1, 0.53.2, 0.54.0, 0.54.1, 0.54.2, 0.55.0, 0.55.1, 0.56.0, 0.56.1, 0.57.0, 0.58.0, 0.58.1, 0.59.0, 0.60.0, 0.60.1, 0.60.2, 0.61.0, 0.61.1, 0.61.2, 0.62.0, 0.63.0, 0.64.0, 0.65.0, 0.65.1
All unaffected versions: 0.65.2, 0.65.3, 0.66.0, 0.66.1, 0.67.0, 0.68.0, 0.68.1, 0.68.2, 0.69.0, 0.70.0, 0.70.1, 0.71.0, 0.72.0, 0.73.0, 0.74.0, 0.74.1, 0.75.0, 0.75.1, 0.75.2, 0.76.0, 0.77.0, 0.77.1, 0.78.0, 0.79.0, 0.79.1, 0.80.0, 0.81.0, 0.82.0, 0.83.0, 0.84.0, 0.85.0, 0.85.1, 0.85.2, 0.86.0, 0.87.0, 0.88.0, 0.89.0, 0.89.1, 0.90.0, 0.90.1, 0.91.0, 0.92.0, 0.93.0, 0.94.0, 0.94.1, 0.95.0, 0.95.1, 0.95.2, 0.96.0, 0.96.1, 0.97.0, 0.98.0, 0.99.0, 0.99.1, 0.100.0, 0.100.1, 0.101.0, 0.101.1, 0.102.0, 0.103.0, 0.103.1, 0.103.2, 0.104.0, 0.104.1, 0.105.0, 0.106.0, 0.107.0, 0.108.0, 0.109.0, 0.109.1, 0.109.2, 0.110.0, 0.110.1, 0.110.2, 0.110.3, 0.111.0, 0.111.1, 0.112.0, 0.112.1, 0.112.2, 0.112.3, 0.112.4, 0.113.0, 0.114.0, 0.114.1