CVE-2025-53539 Details
Description
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.
A denial-of-service vulnerability has been identified in FastAPI Guard versions through 3.0.0. The issue arises in the library's middleware that detects penetration attempts by scanning incoming requests with regular expressions. Some of these regex patterns are highly inefficient, leading to polynomial complexity backtracks when processing specially crafted inputs. This vulnerability can be exploited by sending a single request containing a payload that causes high CPU usage, potentially making the service unresponsive for hours.
Users can upgrade to FastAPI Guard version 3.0.1 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jul 7, 2025References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-1333 | Inefficient Regular Expression Complexity | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| fastapi-guard fastapi guard | < 3.0.1 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Dec 31, 2025 | Initial Analysis | [email protected] |
| Jul 7, 2025 | New CVE Received | [email protected] |