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

MinIO is a high-performance object storage system. Starting in RELEASE.2023-05-18T00-05-36Z and prior to RELEASE.2026-04-11T03-20-12Z, 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. 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). Users of the open-source `minio/minio` project should upgrade to MinIO AIStor `RELEASE.2026-04-11T03-20-12Z` or later. If upgrading is not immediately possible, block unsigned-trailer requests at the load balancer. Reject any request containing `X-Amz-Content-Sha256: STREAMING-UNSIGNED-PAYLOAD-TRAILER` at the reverse proxy or WAF layer. Clients can use `STREAMING-AWS4-HMAC-SHA256-PAYLOAD-TRAILER` (the signed variant) instead. Alternatively, restrict WRITE permissions. Limit `s3:PutObject` grants to trusted principals. While this reduces the attack surface, it does not eliminate the vulnerability since any user with WRITE permission can exploit it with only their access key.

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MinIO 授权问题漏洞

MinIO是美国MinIO公司的一款开源的对象存储服务器。该产品支持构建用于机器学习、分析和应用程序数据工作负载的基础架构。 MinIO存在授权问题漏洞，该漏洞源于STREAMING-UNSIGNED-PAYLOAD-TRAILER代码路径存在身份验证绕过，允许知道有效访问密钥的用户无需知道密钥或提供有效签名即可向任意存储桶写入对象。以下版本受到影响：RELEASE.2023-05-18T00-05-36Z至RELEASE.2026-04-11T03-20-12Z之前版本。

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