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CVE-2025-53539

20
FAUCET Score

CVE-2025-53539 describes a denial-of-service vulnerability in FastAPI Guard, a security library for FastAPI, affecting versions prior to 3.0.1. The flaw stems from inefficient regex patterns used in its penetration attempt detection, which can lead to polynomial complexity backtracks when processing specially crafted inputs. This vulnerability carries a CVSS score of 7.5 (HIGH), indicating a network-based attack with low complexity that can result in high availability impact. Currently, there is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 3.0.1CPE matchmatch criteria
cpe:2.3:a:fastapi-guard:fastapi_guard:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

6.9MEDIUM

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
VS Confidentiality
NONE
VS Integrity
NONE
VS Availability
LOW
SS Confidentiality
NONE
SS Integrity
NONE
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.42%
Probability of exploitation in next 30 days
EPSS Percentile
34.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0042 is in the 14th percentile among its peer group of 51,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
pippatch availablevia ghsa
Product: fastapi-guardFixed in: 3.0.1

Vendor Advisories (1)

pipGHSA-j47q-rc62-w448medium

fastapi-guard is vulnerable to ReDoS through inefficient regex

Jul 7, 2025

References

github.com / rennf93/fastapi-guard/commit/d9d50e8130b7b434cdc1b001b8cfd03a06729f7f
Patch
github.com / rennf93/fastapi-guard/security/advisories/GHSA-j47q-rc62-w448
ExploitVendor Advisory