Executive brief
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.
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