MinIO Signature Verification signature-v4-utils.go extractSignedHeaders privileges management

Summaryinfo

A vulnerability was found in MinIO. It has been declared as critical. Affected by this issue is the function extractSignedHeaders of the file cmd/signature-v4-utils.go of the component Signature Verification. Executing a manipulation can lead to privileges management. This vulnerability appears as CVE-2026-97731. The attack may be performed from remote. There is no available exploit. It is advisable to implement a patch to correct this issue.

Detailsinfo

A vulnerability has been found in MinIO (version now known) and classified as critical. This vulnerability affects the function extractSignedHeaders of the file cmd/signature-v4-utils.go of the component Signature Verification. The manipulation with an unknown input leads to a privileges management vulnerability. The CWE definition for the vulnerability is CWE-269. The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

MinIO through 7aac2a2 does not verify that every x-amz-* header present on a request also appears in the client-supplied X-Amz-SignedHeaders list. extractSignedHeaders() in cmd/signature-v4-utils.go iterates only the claimed list and never enumerates the headers that actually arrived, and thus a header that arrives unsigned is neither hashed into the canonical request nor rejected. Because cmd/api-router.go dispatches CopyObject on the presence of x-amz-copy-source alone, the holder of a presigned PUT URL scoped to a single object can add that header to the unmodified URL and cause a server-side copy, executed as the signer, of any object the signing key can read. A grant to write one object becomes a read of every bucket that key can reach. Amazon S3 rejects the equivalent request with HTTP 403 AccessDenied. The minio/minio GitHub repository was archived in April 2026; pgsty/silo before 1233254 is also affected.

The advisory is shared for download at silo.pgsty.com. This vulnerability was named CVE-2026-97731 since 09/25/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1068.

Applying the patch 7aac2a2c5b7c882e68c1ce017d8256be2feea27f is able to eliminate this problem.

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• MinIO

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