GHSA-8h2j-cgx8-6xv7
Vulnerability from github
Published
2021-06-10 15:43
Modified
2024-09-20 17:18
Severity ?
8.2 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
8.8 (High) - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N
Summary
Cross-Site Request Forgery (CSRF) in FastAPI
Details

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 security@tiangolo.com

Show details on source website

To clipboard 

{
   affected: [
      {
         package: {
            ecosystem: "PyPI",
            name: "fastapi",
         },
         ranges: [
            {
               events: [
                  {
                     introduced: "0",
                  },
                  {
                     fixed: "0.65.2",
                  },
               ],
               type: "ECOSYSTEM",
            },
         ],
      },
   ],
   aliases: [
      "CVE-2021-32677",
   ],
   database_specific: {
      cwe_ids: [
         "CWE-352",
      ],
      github_reviewed: true,
      github_reviewed_at: "2021-06-09T13:34:54Z",
      nvd_published_at: "2021-06-09T18:15:00Z",
      severity: "HIGH",
   },
   details: "### Impact\n\nFastAPI 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.\n\nIn 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`).\n\nSo, a request with a content type of `text/plain` containing JSON data would be accepted and the JSON data would be extracted.\n\nBut requests with content type `text/plain` are exempt from [CORS](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS) preflights, for being considered [Simple requests](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#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.\n\n### Patches\n\nThis is fixed in FastAPI `0.65.2`.\n\nThe 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`.\n\n### Workarounds\n\nIt's best to upgrade to the latest FastAPI.\n\nBut 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.\n\n### References\n\n* [CORS on Mozilla web docs](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS)\n* [This answer on StackExchange](https://security.stackexchange.com/questions/157528/ways-to-bypass-browsers-cors-policy/157531#157531)\n* [OWASP CSRF](https://owasp.org/www-community/attacks/csrf)\n* Fixed in PR [#2118](https://github.com/tiangolo/fastapi/pull/2118)\n\n### For more information\n\nIf you have any questions or comments, write to [security@tiangolo.com](mailto:security@tiangolo.com)",
   id: "GHSA-8h2j-cgx8-6xv7",
   modified: "2024-09-20T17:18:26Z",
   published: "2021-06-10T15:43:54Z",
   references: [
      {
         type: "WEB",
         url: "https://github.com/tiangolo/fastapi/security/advisories/GHSA-8h2j-cgx8-6xv7",
      },
      {
         type: "ADVISORY",
         url: "https://nvd.nist.gov/vuln/detail/CVE-2021-32677",
      },
      {
         type: "WEB",
         url: "https://github.com/tiangolo/fastapi/commit/fa7e3c996edf2d5482fff8f9d890ac2390dede4d",
      },
      {
         type: "WEB",
         url: "https://github.com/pypa/advisory-database/tree/main/vulns/fastapi/PYSEC-2021-100.yaml",
      },
      {
         type: "PACKAGE",
         url: "https://github.com/tiangolo/fastapi",
      },
      {
         type: "WEB",
         url: "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MATAWX25TYKNEKLDMKWNLYDB34UWTROA",
      },
   ],
   schema_version: "1.4.0",
   severity: [
      {
         score: "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N",
         type: "CVSS_V3",
      },
      {
         score: "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N",
         type: "CVSS_V4",
      },
   ],
   summary: "Cross-Site Request Forgery (CSRF) in FastAPI",
}


Log in or create an account to share your comment.

Security Advisory comment format.

This schema specifies the format of a comment related to a security advisory.

UUIDv4 of the comment
UUIDv4 of the Vulnerability-Lookup instance
When the comment was created originally
When the comment was last updated
Title of the comment
Description of the comment
The identifier of the vulnerability (CVE ID, GHSA-ID, PYSEC ID, etc.).



Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
  • Confirmed: The vulnerability is confirmed from an analyst perspective.
  • Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
  • Patched: This vulnerability was successfully patched by the user reporting the sighting.
  • Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
  • Not confirmed: The user expresses doubt about the veracity of the vulnerability.
  • Not patched: This vulnerability was not successfully patched by the user reporting the sighting.