Auth bypass in Rustfs
CVE-2026-40937
RustFS is a distributed object storage system built in Rust. Prior to 1.0.0-alpha.94, all four notification target admin API endpoints in `rustfs/src/admin/handlers/event.rs` use a `check_permissions` helper that validates authentication only (access key + session token), without performing any admin-action authorization via `validate_admin_request`. Every other admin handler in the codebase correctly calls `validate_admin_request` with a specific `AdminAction`. This is the only admin handler file that skips authorization. A non-admin user can overwrite a shared admin-defined notification target by name, causing subsequent bucket events to be delivered to an attacker-controlled endpoint. This enables cross-user event interception and audit evasion. 1.0.0-alpha.94 contains a patch.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.3 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L.
EPSS exploit prediction
EPSS: 0.005 (39.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 40th percentile — 39.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
- Rustfs — versions < 1.0.0-alpha.94, 1.0.0
Weakness classification (CWE)
References
- github.com/rustfs/rustfs/security/advisories/GHSA-pfcq-4gjr-6gjm (Mitigation, Vendor Advisory)
- github.com/rustfs/rustfs/releases/tag/1.0.0-alpha.94 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-40937?
- CVE-2026-40937 is a high-severity vulnerability in Rustfs, classified under Missing Authorization. CVSS score: 8.3/10. Published 2026-04-22.
- How severe is CVE-2026-40937?
- High severity. CVSS v3 base score is 8.3 out of 10.