CVE-2025-54365

fastapi-guard patch contains bypassable RegEx

fastapi-guard is a security library for FastAPI that provides middleware to control IPs, log requests, detect penetration attempts and more. In version 3.0.1, the regular expression patched to mitigate the ReDoS vulnerability by limiting the length of string fails to catch inputs that exceed this limit. This type of patch fails to detect cases in which the string representing the attributes of a <script> tag exceeds 100 characters. As a result, most of the regex patterns present in version 3.0.1 can be bypassed. This is fixed in version 3.0.2.

Affected

rennf93 · fastapi-guard

CVSS v4.0 GITHUB

7.8 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:P/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

CVSS v4.0 GitHub

7.8 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:P

CVSS v3.1 NVD

7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

0.81% chance of exploitation in the next 30 days, 56th percentile

Published

2025-07-23

Updated

2025-07-24

Proof-of-concept exploits (2)

• rennf93/fastapi-guard/security/advisories/GHSA-rrf6-pxg8-684g
• advisories/GHSA-rrf6-pxg8-684g

Security advisories

• rennf93/fastapi-guard/commit/0829292c322d33dc14ab00c5451c5c138148035a

References

• CVE Record
• NVD entry