Intel

AIKIDO-2026-10612

fastapi-guard is vulnerable to Security pipeline bypass via CORS preflight short-circuit

Security pipeline bypass via CORS preflight short-circuit Pre-CVE
Found by Aikido Intel before public disclosure or CVE publication.
Published Apr 28, 2026

50

Medium Risk

This Affects:

pythonfastapi-guard
5.0.0 - 5.2.0
Fixed in 6.0.0
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TL;DR

Affected versions of this package are vulnerable to a security-check bypass on CORS preflight requests. Because the library's security middleware runs after the CORS layer, browser preflight requests skip IP banning, rate limiting, and suspicious-pattern detection, letting attackers probe the allowed origins and methods without triggering the protections.

Who does this affect?

You are affected if you are using a version that falls within the vulnerable range.

Background info

fastapi-guard is vulnerable to Security pipeline bypass via CORS preflight short-circuit in versions 5.0.0 - 5.2.0.

How to fix this

Upgrade the fastapi-guard library to the patch version.