CVE-2025-53539: Fastapi-Guard Fastapi Guard

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

FastAPI Guard is a security library for FastAPI that provides middleware to control IPs, log requests, and detect penetration attempts. fastapi-guard's penetration attempts detection uses regex to scan incoming requests. However, some of the regex patterns used in detection are extremely inefficient and can cause polynomial complexity backtracks when handling specially crafted inputs. This vulnerability is fixed in 3.0.1.

Affected products

• Fastapi-Guard Fastapi Guard: before 3.0.1 (fixed in 3.0.1)

Published 2025-07-07. Last modified 2026-06-17.