OpaMiddleware does not filter HTTP OPTIONS requests
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Information disclosure
- Confidentiality · integrity · availability
- Low · None · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-204.
Summary
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.
Why it matters now
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
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| busykoala | fastapi-opa | before 2.0.1 | 2.0.1 | Patch available | CNA |
| — | fastapi-opa (PyPI) | before 2.0.1 | 2.0.1 | Patch available | GHSA-5f5c-8rvc-j8wf |
- fastapi-opa Vendorbusykoala Affected before 2.0.1 Fixed in 2.0.1 Patch available CNA
- fastapi-opa (PyPI) Vendor— Affected before 2.0.1 Fixed in 2.0.1 Patch available GHSA-5f5c-8rvc-j8wf
Remediation
- Fix · CNA fastapi-opa (busykoala) Fixed in 2.0.1
- Fix · GHSA-5f5c-8rvc-j8wf fastapi-opa (PyPI) Fixed in 2.0.1 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2024-40627
- 2026-10-03 Alias added: GHSA-5f5c-8rvc-j8wf
References
Other 5
- 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
- https://github.com/busykoala/fastapi-opa/commit/9458845a6f6f414c0b79587fae83d7f14d74dfb4
- https://github.com/busykoala/fastapi-opa
Sources
- CVE-2024-40627 · CVE Program
- CVE-2024-40627 · NVD
- FIRST EPSS
- GHSA-5f5c-8rvc-j8wf · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences