# CVE-2025-31489: MinIO performs incomplete signature validation for unsigned-trailer uploads

- Exploited (CISA KEV): no
- Published: 2025-04-03
- CVSS: 8.7 HIGH (v4.0)
- EPSS: 2.5% (85th percentile)
- CWE: CWE-347

MinIO is a High Performance Object Storage released under GNU Affero General Public License v3.0. The signature component of the authorization may be invalid, which would mean that as a client you can use any arbitrary secret to upload objects given the user already has prior WRITE permissions on the bucket. Prior knowledge of access-key, and bucket name this user might have access
to - and an access-key with a WRITE permissions is necessary. However with relevant information in place, uploading random objects to buckets is trivial and easy via curl. This issue is fixed in RELEASE.2025-04-03T14-56-28Z.

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | Blocks by default | 2025-05-05 | 32 |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | No public claim | — | — |
| Fastly | Before feed history | — | — |
| F5 | No public claim | — | — |
| Akamai | No public source | — | — |
| OWASP CRS | No public claim | — | — |

### Cloudflare

- 2025-05-05 · new · rule 5eb7ed601e6844828b9bdb05caa7b208 · default Block
  > MinIO - Auth Bypass - CVE:CVE-2025-31489. Previous action: Log. New action: Block. This is a New Detection
  Source: https://developers.cloudflare.com/changelog/post/2025-05-05-waf-release/

## Our test (measured)

- OWASP Core Rule Set 4.25.0, paranoia level 1, anomaly threshold 5, default CRS settings: blocked (1 of 1 requests blocked), template CVE-2025-31489, 2026-11-02
- OWASP Core Rule Set 4.25.0, paranoia level 2, anomaly threshold 5, default CRS settings: blocked (1 of 1 requests blocked), template CVE-2025-31489, 2026-11-02

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2025-31489 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2025-31489