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CVE-2026-39360· NVD / CVE Program· CNA GitHub_M

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

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.

MediumCVSS 5.3 · v4.0—No exploit No fix recorded
Published
Apr 7, 2026
Updated
Jul 24, 2026
EPSS
0.3% · 18th percentile
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Report tools

JSON

Action score

21

Monitor

Low priority for now.

CVSS
21 / 40 · 5.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
5.3
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

VendorProduct
rustfsrustfs

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • rustfs rustfs1.0.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • rustfs rustfs

    • < alpha.90affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
crates.iorustfsup to and including 0.0.2—

Same product

rustfs: all records

Other highest-scoring records for the same primary product.

  • CVE-2025-68926RustFS has a gRPC Hardcoded Token Authentication Bypass
    49Plan
  • CVE-2026-45039RustFS: Internode RPC HMAC secret falls back to public default credential, enabling peer impersonation
    39Monitor
  • CVE-2026-45043RustFS: ImportIam Allows Creation of Backdoor Service Accounts Under Any Parent Including Root
    37Monitor
  • CVE-2025-68705RustFS Path Traversal Vulnerability
    37Monitor
  • CVE-2026-27607RustFS's Missing Post Policy Validation leads to Arbitrary Object Write
    36Monitor
  • CVE-2026-73284RustFS: AddServiceAccount Handler Allows Creation of Root-Parent Service Accounts
    35Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-4093715 days apartRustFS missing admin authorization on notification target endpoints, which allows unauthenticated configuration of event webhooks
    33Monitor
  • CVE-2026-5518980 days apartRustFS: FTP frontend skips IAM authorization on object reads
    30Monitor
  • CVE-2026-73265127 days apartRustFS: Version-specific object reads authorize the non-version action
    26Monitor
  • CVE-2026-73287127 days apartRustFS: FTPS MKD bypasses IAM CreateBucket authorization
    21Monitor
  • CVE-2026-5583880 days apartRustFS: Missing admin authorization on /rustfs/admin/v3/metrics allows any authenticated user to read server metrics
    17Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
X

Weakness class (CWE)

CWE-862 · Missing Authorization

CVSS 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

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Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

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