Medium severity · published Apr 7, 2026
CVE-2026-39360
RustFS has an authorization bypass in multipart UploadPartCopy enables cross-bucket object exfiltration
4.3
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
Low
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 10% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
RU
rustfs · rustfs
< alpha.90 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39360
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-39360
Exploit
https://github.com/rustfs/rustfs/security/advisories/GHSA-mx42-j6wv-px98
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