CVE-2025-53539

ReDoS in fastapi-guard's penetration attempts detector

Published Jul 7, 2025 CVSS 4.0 · 6.9 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
EUVD EUVD EUVD-2025-20307 fastapi-guard is vulnerable to ReDoS through inefficient regex
Github GHSA Github GHSA GHSA-j47q-rc62-w448 fastapi-guard is vulnerable to ReDoS through inefficient regex
History
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'}

Type Values Removed Values Added
Metrics epss

{'score': 0.00042}

epss

{'score': 0.00055}

Type Values Removed Values Added
Metrics ssvc

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

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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jul 7, 2025, 8:51 PM
Reserved
Jul 2, 2025, 3:15 PM
Status
Analyzed
Published
Jul 7, 2025, 8:15 PM
Modified
Jun 17, 2026, 9:38 AM