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CVE-2025-53539— ReDoS in fastapi-guard's penetration attempts detector

Quick assessment

Affected
rennf93 fastapi-guard
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

fastapi-guard是Renzo F个人开发者的一个FastAPI的安全库，提供中间件来控制IP、记录请求和检测渗透尝试。 fastapi-guard 3.0.1之前版本存在安全漏洞，该漏洞源于正则表达式模式效率低下，可能导致多项式复杂度回溯。

AI Predicted 5.3 Difficulty: Easy EPSS 0.42% · P35

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2025-53539

Vulnerability Information
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Vulnerability Title
ReDoS in fastapi-guard's penetration attempts detector
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1333
Source: CVE Program / CVE List V5
Vulnerability Title
fastapi-guard 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
fastapi-guard是Renzo F个人开发者的一个FastAPI的安全库，提供中间件来控制IP、记录请求和检测渗透尝试。 fastapi-guard 3.0.1之前版本存在安全漏洞，该漏洞源于正则表达式模式效率低下，可能导致多项式复杂度回溯。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
rennf93 fastapi-guard < 3.0.1 -

II. Public POCs for CVE-2025-53539

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III. Intelligence Information for CVE-2025-53539

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Vendor Advisories for CVE-2025-53539 (1)

IV. Related Vulnerabilities

Same product: fastapi-guard
Same vendor: rennf93
Same weakness: CWE-1333

V. Comments for CVE-2025-53539

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