CVE-2026-27607 RustFS's Missing Post Policy Validation leads to Arbitrary Object Write
Attackers can bypass upload policy restrictions to write arbitrary objects, spoof content types, and exhaust storage in RustFS object storage systems.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-27607?
CVE-2026-27607 is a high-severity missing authorization vulnerability in rustfs, published on 25 Feb 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. In versions 1.0.0-alpha.56 through 1.0.0-alpha.82, RustFS does not validate policy conditions in presigned POST uploads (PostObject), allowing attackers to bypass content-length-range, starts-with, and Content-Type constraints. This enables unauthorized file uploads exceeding size limits, uploads to arbitrary object keys, and content-type spoofing, potentially leading to storage exhaustion, unauthorized data access, and security bypasses. Version 1.0.0-alpha.83 fixes the issue.
Which versions are affected by CVE-2026-27607?
2 open source packages ship an affected version, including rustfs. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
rustfs crates.io | From 1.0.0-alpha.56 | 1.0.0-alpha.83 |
rustfs crates.io | From 1.0.0-alpha.56 | 1.0.0-alpha.83 |
Products include Rustfs Rustfs.
How do I fix CVE-2026-27607?
Upgrade rustfs to 1.0.0-alpha.83 or later.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-27607 being exploited?
There is no known exploitation of CVE-2026-27607 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in rustfs
- CVE-2025-68926 RustFS has a gRPC Hardcoded Token Authentication Bypass
- CVE-2026-27822 Rust has Critical Stored XSS in Preview Modal, leading to Administrative Account Takeover
- CVE-2025-68705 RustFS Path Traversal Vulnerability
- CVE-2026-40937 RustFS: Missing admin authorization on notification target endpoints allows unauthenticated configuration of event webhooks
- CVE-2026-21862 RustFS sourceIp bypass via spoofed X-Forwarded-For/Real-IP headers
Sources
Also known as GHSA-w5fh-f8xh-5x3p.