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CVE-2026-46685: RustFS: Reflective CORS with credentials on S3 listener; unauthenticated license metadata endpoint on console

• Severity: medium (CVSS 6.0 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-28 · updated 2026-06-17
• Weakness: CWE-306

Description

RustFS is a distributed object storage system built in Rust. Prior to 1.0.0-beta.2, when RUSTFS_CORS_ALLOWED_ORIGINS is unset, the RustFS S3 listener's ConditionalCorsLayer reflects any request Origin value back as Access-Control-Allow-Origin and also sets Access-Control-Allow-Credentials: true and Access-Control-Allow-Headers: * on responses, including preflight responses and error responses. This creates a permissive cross-domain policy with untrusted origins. A browser visiting an attacker-controlled page can issue credentialed cross-origin requests to a reachable RustFS deployment and read the response when the victim browser has ambient credentials for the RustFS origin, such as saved HTTP Basic Auth credentials, reverse-proxy SSO cookies, or TLS client certificates. This vulnerability is fixed in 1.0.0-beta.2.

Affected products

• rustfs: before 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

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