Cloudanix VulnDB

GHSA-hv4r-mvr4-25vw

High · 8.2

MinIO has an Unauthenticated Object Write via Query-String Credential Signature Bypass in Unsigned-Trailer Uploads

CVSS

8.2

EPSS

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Published

Apr 14, 2026

CISA due date

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The record

_What kind of vulnerability is it? Who is impacted?_ An authentication bypass vulnerability in MinIO's `STREAMING-UNSIGNED-PAYLOAD-TRAILER` code path allows any user who knows a valid access key to write arbitrary objects to any bucket without knowing the secret key or providing a valid cryptographic signature. Any MinIO deployment is impacted. The attack requires only a valid access key (the well-known default `minioadmin`, or any key with WRITE permission on a bucket) and a target bucket name. `PutObjectHandler` and `PutObjectPartHandler` call `newUnsignedV4ChunkedReader` with a signature verification gate based solely on the presence of the `Authorization` header: ```go newUnsignedV4ChunkedReader(r, true, r.Header.Get(xhttp.Authorization) != "") ``` Meanwhile, `isPutActionAllowed` extracts credentials from either the `Authorization` header or the `X-Amz-Credential` query parameter, and trusts whichever it finds. An attacker omits the `Authorization` header and supplies credentials exclusively via the query string. The signature gate evaluates to `false`, `doesSignatureMatch` is never called, and the request proceeds with the permissions of the impersonated access key. This affects `PutObjectHandler` (standard and tables/warehouse bucket paths) and `PutObjectPartHandler` (multipart uploads). **Affected components:** `cmd/object-handlers.go` (`PutObjectHandler`), `cmd/object-multipart-handlers.go` (`PutObjectPartHandler`).

Affected packages

Ecosystem Package Introduced Fixed

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