Vulnerability · Published Apr 7, 2026 · Assigned by GitHub_M

CVE-2026-39360RustFS has an authorization bypass in multipart UploadPartCopy enables cross-bucket object exfiltration

Medium 5.3

In plain English

A medium-severity missing authorization in rustfs from rustfs. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 11% of all known vulnerabilities).

Severity (CVSS 4.0)5.3Medium

Exploit odds (30 days)0.2%top 89.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

RustFS is a distributed object storage system built in Rust. Prior to alpha.90, RustFS contains a missing authorization check in the multipart copy path (UploadPartCopy). A low-privileged user who cannot read objects from a victim bucket can still exfiltrate victim objects by copying them into an attacker-controlled multipart upload and completing the upload. This breaks tenant isolation in multi-user / multi-tenant deployments. This vulnerability is fixed in alpha.90.

Affected products (as reported)

Vendor	Product	Versions
rustfs	rustfs	< alpha.90

Weakness: CWE-862 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

References

https://github.com/rustfs/rustfs/security/advisories/GHSA-mx42-j6wv-px98 x_refsource_CONFIRM