# CVE-2026-46685: RustFS permissive CORS policy in S3 listener

Source: https://junglewise.ai/threats/cve-2026-46685-rustfs-permissive-cors-policy-in-s3-listener  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-28. Updated: 2026-05-28  
License: CC BY 4.0 with a link back

CVE-2026-46685 · Severity: info · CVSS 6 · Published 2026-05-28

RustFS is a distributed storage system used to store and manage large amounts of data. A security flaw in its default configuration allows malicious websites to trick a user's browser into making unauthorized requests to the storage system. If a user is logged into RustFS, an attacker could potentially read their private files or data through the victim's browser.

## Quick answers

**Is CVE-2026-46685 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-46685 being exploited in the wild.

**How severe is CVE-2026-46685?** Informational severity, with a CVSS score of 6, published 28 May 2026.

**Which products and versions are affected?** RustFS RustFS < 1.0.0-beta.2.

**Is there a fix for CVE-2026-46685?** A patch was published on 2026-05-28: Fixed in version 1.0.0-beta.2 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-46685 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-46685?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A permissive Cross-Origin Resource Sharing (CORS) policy exists in the RustFS S3 listener's ConditionalCorsLayer. When the RUSTFS_CORS_ALLOWED_ORIGINS environment variable is unset, the application reflects any 'Origin' header from a request back into the 'Access-Control-Allow-Origin' response header. It simultaneously sets 'Access-Control-Allow-Credentials' to true. This combination allows an attacker-controlled website to perform credentialed requests (using cookies, Basic Auth, or TLS certificates) via a victim's browser and read the resulting responses. The vulnerability is rooted in rustfs/src/server/layer.rs and is fixed in version 1.0.0-beta.2 by changing the default behavior to emit no CORS headers when unconfigured.

## Affected products

- RustFS RustFS < 1.0.0-beta.2

## Timeline

- 2026-05-25: advisory: GitHub Security Advisory published
- 2026-05-28: disclosed: CVE published to NVD
- 2026-05-28: patched: Fixed in version 1.0.0-beta.2

## References

- [https://github.com/rustfs/rustfs/security/advisories/GHSA-x5xv-223c-8vm7](https://github.com/rustfs/rustfs/security/advisories/GHSA-x5xv-223c-8vm7)