CVE-2021-32677

Published Jun 9, 2021

Last updated 9 months ago

Overview

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.
Source: security-advisories@github.com
NVD status: Modified

Risk scores

CVSS 3.1

Type: Primary
Base score: 8.1
Impact score: 5.2
Exploitability score: 2.8
Vector string: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Severity: HIGH

CVSS 2.0

Type: Primary
Base score: 5.8
Impact score: 4.9
Exploitability score: 8.6
Vector string: AV:N/AC:M/Au:N/C:P/I:P/A:N

Weaknesses

security-advisories@github.com: CWE-352

Hype score: Not currently trending

Configurations

[
  {
    "nodes": [
      {
        "negate": false,
        "cpeMatch": [
          {
            "criteria": "cpe:2.3:a:tiangolo:fastapi:*:*:*:*:*:*:*:*",
            "vulnerable": true,
            "matchCriteriaId": "60506886-D0E8-4F9C-B900-D373A4435A4D",
            "versionEndExcluding": "0.65.2"
          }
        ],
        "operator": "OR"
      }
    ]
  },
  {
    "nodes": [
      {
        "negate": false,
        "cpeMatch": [
          {
            "criteria": "cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*",
            "vulnerable": true,
            "matchCriteriaId": "A930E247-0B43-43CB-98FF-6CE7B8189835"
          }
        ],
        "operator": "OR"
      }
    ]
  }
]

Overview

Risk scores

CVSS 3.1

CVSS 2.0

Weaknesses

Social media

Configurations

References