---
id: CVE-2025-14546
aliases:
  - GHSA-hp6r-r9vc-q8wx
  - PYSEC-2026-1362
title: >-
  FastAPI SSP is vulnerable to Cross-site Request Forgery (CSRF) through
  improper OAuth parameter validation
summary: >-
  FastAPI SSP is vulnerable to Cross-site Request Forgery (CSRF) through
  improper OAuth parameter validation
severity: medium
cvss: 6.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N'
vendor: fastapi-sso
product: fastapi-sso
ecosystem: pip
affected:
  - fastapi-sso < 0.19.0
patched:
  - fastapi-sso 0.19.0
published: '2025-12-19'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:31.957663246Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-hp6r-r9vc-q8wx'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2025-14546'
  - url: 'https://github.com/tomasvotava/fastapi-sso/issues/266'
  - url: >-
      https://github.com/tomasvotava/fastapi-sso/commit/6117d1a5ad498ba57d671e8a059ebe20db5abe02
  - url: 'https://github.com/tomasvotava/fastapi-sso'
  - url: 'https://security.snyk.io/vuln/SNYK-PYTHON-FASTAPISSO-14386403'
tags:
  - osv
  - pip
epss: 0.00359
epssPercentile: 0.29698
ingestedAt: '2026-07-08T18:25:50.293Z'
---

## Overview

Versions of the package fastapi-sso before 0.19.0 are vulnerable to Cross-site Request Forgery (CSRF) due to the improper validation of the OAuth state parameter during the authentication callback. While the get_login_url method allows for state generation, it does not persist the state or bind it to the user's session. Consequently, the verify_and_process method accepts the state received in the query parameters without verifying it against a trusted local value. This allows a remote attacker to trick a victim into visiting a malicious callback URL, which can result in the attacker's account being linked to the victim's internal account.

## Affected packages

- `fastapi-sso < 0.19.0`

## Remediation

Upgrade to a patched release:

- `fastapi-sso 0.19.0`