Use of Less Trusted Source Affecting fastapi-guard package, versions [,2.0.0)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PYTHON-FASTAPIGUARD-10245561
- published26 May 2025
- disclosed6 May 2025
- creditamooryx
Introduced: 6 May 2025
NewCVE-2025-46814 (opens in a new tab)How to fix?
Upgrade fastapi-guard to version 2.0.0 or higher.
Overview
fastapi-guard is a Security library for FastAPI to control IPs and more.
Affected versions of this package are vulnerable to Use of Less Trusted Source via the manipulation of the X-Forwarded-For header. An attacker can inject arbitrary IP addresses into the request by manipulating this header. This can lead to bypassing IP-based access controls, misleading logging systems, and impersonating trusted clients.
PoC
Run the FastAPI application locally:
uvicorn main:app --host 0.0.0.0 --port 8000
Send a crafted request with a manipulated X-Forwarded-For header:
curl -i http://127.0.0.1:8000/ -H "X-Forwarded-For: 8.8.8.8"