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.

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact Low

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00069.

Exploitation poc

Automatable no

Technical Impact partial

Affected Vendors & Products

Vendors Products
Fastapi-guard
  • Fastapi Guard

Configuration 1 [-]

cpe:2.3:a:fastapi-guard:fastapi_guard:*:*:*:*:*:*:*:*

No data.

No data.

References
Link Providers
https://github.com/rennf93/fastapi-guard/commit/d9d50e8130b7b434cdc1b001b8cfd03a06729f7f cve-icon cve-icon
https://github.com/rennf93/fastapi-guard/security/advisories/GHSA-j47q-rc62-w448 cve-icon cve-icon
History

Wed, 31 Dec 2025 17:15:00 +0000

Type Values Removed Values Added
First Time appeared Fastapi-guard
Fastapi-guard fastapi Guard
CPEs cpe:2.3:a:fastapi-guard:fastapi_guard:*:*:*:*:*:*:*:*
Vendors & Products Fastapi-guard
Fastapi-guard fastapi Guard
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Sun, 13 Jul 2025 13:45:00 +0000

Type Values Removed Values Added
Metrics epss

{'score': 0.00042}

 epss

{'score': 0.00055}

Mon, 07 Jul 2025 21:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Mon, 07 Jul 2025 19:30:00 +0000

Type Values Removed Values Added
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.
Title ReDoS in fastapi-guard's penetration attempts detector
Weaknesses CWE-1333
References
Metrics cvssV4_0

{'score': 6.9, 'vector': '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'}
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2025-07-07T20:51:58.541Z

Reserved: 2025-07-02T15:15:11.515Z

Link: CVE-2025-53539

cve-icon Vulnrichment

Updated: 2025-07-07T20:51:49.329Z

cve-icon NVD

Status : Analyzed

Published: 2025-07-07T20:15:28.027

Modified: 2025-12-31T17:05:33.607

Link: CVE-2025-53539

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.