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TI-2025-34178 Aliases CVE-2025-54365GHSA-rrf6-pxg8-684g

fastapi-guard patch contains bypassable RegEx

Priority HIGH 73CWE-185Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Denial of service
Confidentiality · integrity · availability
None · Low · High
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-1333.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00871 59th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed fastapi-guard (rennf93): 3.0.2fastapi-guard (PyPI): 3.0.2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
rennf93fastapi-guard3.0.1 to before 3.0.23.0.2Patch availableCNA
—fastapi-guard (PyPI)3.0.1 to before 3.0.23.0.2Patch availableGHSA-rrf6-pxg8-684g
  • fastapi-guard Vendorrennf93 Affected 3.0.1 to before 3.0.2 Fixed in 3.0.2 Patch available CNA
  • fastapi-guard (PyPI) Vendor— Affected 3.0.1 to before 3.0.2 Fixed in 3.0.2 Patch available GHSA-rrf6-pxg8-684g

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:fastapi-guard:fastapi_guard:3.0.1:*:*:*:*:*:*:*3.0.1Vulnerablerennf93
  • cpe:2.3:a:fastapi-guard:fastapi_guard:3.0.1:*:*:*:*:*:*:* Versions 3.0.1 Vulnerable ·rennf93

Remediation

  • Fix · CNA fastapi-guard (rennf93) Fixed in 3.0.2
  • Fix · GHSA-rrf6-pxg8-684g fastapi-guard (PyPI) Fixed in 3.0.2 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2025-54365
  2. 2026-10-03 Alias added: GHSA-rrf6-pxg8-684g

References

Exploit 1

Patch 2

Advisory 1

Other 1

  • TI-2025-29447 FastAPI Guard Remote Header Injection via X-Forwarded-For Manipulation CVSS 3.1HIGH 7.5
  • TI-2025-33483 ReDoS in fastapi-guard's penetration attempts detector CVSS 4.0MEDIUM 6.9

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences