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

> A missing authorization check in RustFS allows low-privileged users to exfiltrate objects from other buckets via multipart copy operations.

- **Severity:** Medium 5.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Apr 2026
- **Updated:** 7 Apr 2026
- **Also known as:** GHSA-mx42-j6wv-px98

## What is CVE-2026-39360?

CVE-2026-39360 is a medium-severity missing authorization vulnerability in rustfs, published on 7 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### 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.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-39360?

2 open source packages ship an affected version, including rustfs. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `rustfs` | crates.io | All versions to 0.0.2 | None |
| `rustfs` | crates.io | All versions to 0.0.2 | None |

Products: Rustfs Rustfs.

## How do I fix CVE-2026-39360?

No fix has been published for CVE-2026-39360 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-39360 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39360 exists.

## Other vulnerabilities in rustfs

- [CVE-2025-68926](https://insights.sbomify.com/CVE-2025-68926/): RustFS has a gRPC Hardcoded Token Authentication Bypass (critical 9.8)
- [CVE-2026-27822](https://insights.sbomify.com/CVE-2026-27822/): Rust has Critical Stored XSS in Preview Modal, leading to Administrative Account Takeover (critical 9.1)
- [CVE-2025-68705](https://insights.sbomify.com/CVE-2025-68705/): RustFS Path Traversal Vulnerability (high 8.8)
- [CVE-2026-40937](https://insights.sbomify.com/CVE-2026-40937/): RustFS: Missing admin authorization on notification target endpoints allows unauthenticated configuration of event webhooks (high 8.3)
- [CVE-2026-27607](https://insights.sbomify.com/CVE-2026-27607/): RustFS's Missing Post Policy Validation leads to Arbitrary Object Write (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39360 and fix it if it is affected.

What it is: CVE-2026-39360 is a medium-severity missing authorization vulnerability in rustfs, published on 7 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39360 exists.

Affected packages and fixed versions:
- rustfs (crates.io): affected all versions up to 0.0.2; no fix listed
- rustfs (crates.io): affected all versions up to 0.0.2; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-39360/ (Markdown: https://insights.sbomify.com/CVE-2026-39360/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39360
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39360
- OSV: https://osv.dev/vulnerability/CVE-2026-39360

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39360/
Summaries are generated and may contain mistakes; the official description above is the record.